Freyja is most often summarized as the Northern goddess of Love and Beauty, and that she is - but she is far, far more than that. Freyja is one of the few Northern gods who may actually have unbroken worship, although modern Northern Paganism is not directly based on whatever folk traditions may have survived to honor her.
Freyja is the Vanadis - the Lady of the Vanir. Her twin brother Freyr is the current Lord of Vanaheim and Alfheim both. Their parents, also twins, are Njordh, Lord of the Sea and his sister, most likely the Earth goddess Nerthus. The lore implies that Freyja was originally married to Freyr before the first war was fought between the Vanir and Aesir. At the end of the war when Freyja, Freyr and Njordh were fostered to the Aesir as hostages in exchange for Honir and Mimir, the Aesir declared the sibling marriages of the Vanir unlawful in Asgard, and arranged new marriages for each of them over time. Freyja's husband among the Aesir is Odr, who has since been lost, his identity and provenance is a true mystery, although one of the most common UPGs is that Odr is or became Odin. Freyja's daughters with Odr are the treasures, Hnoss and Gersemi. In modern practice, we have found that the Vanir recognise both marriages, and Freyja often acts loverly towards Freyr, regarding Gerd not only as sister-in-law, but also as sister-wife. Gerd is the lady of Alfheim, as Freyr's consort, leaving Freyja as the primary ruler in Vanaheim, although she still shares those duties with her brother and parents.
Freyja is indeed a goddess of love and beauty, of sex and fertility. In my experience, love is her primary motivation, and a deep, abiding sense of the beauty of all things is the core of her nature. She encourages self-awareness and self-worth regarding our own beauty and sexuality, and may be anything from achingly gentle to forcefully dominant in showing people what they are worth. I have known her to require people to stand naked in front of a mirror, repeating compliments they can barely stand to say or hear, as she guides them word by word in the act of learning to admire themselves.
She can be called upon to help with fertility in humans and animals especially, as well as the fecundity of the land. Fertility is not a metaphor to Freyja - if you ask for her help with fertility, be very clear what you do and do not want. While human sexuality may be used to empower the land, to drive artistic creativity, to bring those who love each other closer together, or even just for sensual enjoyment, if you start heterosexual fertility magic with Freyja, be quite clear what your boundaries are with regards to pregnancy, and do not be surprised if she is disappointed at the need for barriers. She will respect any boundaries you set for your own body.
Freyja is associated with all female animals, especially domestic animals in heat or giving birth. She has several specific animal associations, as well, each of which illuminate some aspect of her power:
* Her falcon-feathered cloak allows the wearer to fly, usually in the form of a falcon, demonstrating Freyja's connection with shape-shifting magic - an aspect of Seidhr trance magic. Loki often borrows her cloak when he needs to solve a problem for the Aesir.
* A pair of cats work together to draw her cart, proving her sovereignty as a goddess. Diana Paxson suggested the names Bygul and Trjegul - "Bee-gold" and "Tree-Gold" - for Freyja's cats, to honor her connections with honey and amber.
* One of Freyja's titles is "Mare of the Vanir", giving her a connection with horses, and emphasizing her role as a fertility goddess.
* The Vanir in general are connected with swine, and Freyja is no exception; one of her kennings is "Syr", meaning "sow", and she is sometimes depicted riding a boar named Hildisvíni. Swine are also strong fertility symbols.
Freyja's power and beauty are symbolized most strongly by the necklace Brisingamen. The four dwarven smiths, the Brising brothers, forged a golden necklace of unsurpassed beauty, which Freyja could not bear to let pass from her grasp. She offered them every objct of value she could think of in exchange, but they wanted only service - a night in her bed for each of them. Post-Christian interpretations describe her acceptance of these terms as compelled by temptation despite the dwarves being hideous creatures. They describe it as infidelity to Odr, and many surmise that this infidelity is why he went away, leaving Freyja to wander the worlds weeping tears that turned to gold when they touched the land, and amber when they touched water.
I do not believe Odr left in a jealous fit over Freyja's sexuality, nor do I believe Freyja scoffed at the Brisings' request. I believe Freyja accepted their terms with aplomb and showed the dwarves their own beauty, and that doing so was well within her rights, as her husband Odr must have known. She traded for her beautiful golden necklace of power fairly, and in doing so gave us a model for appreciating the value of our own abilities and attributes.
Freyja is a goddess of war and death. She is the first chooser of the slain. She is sometimes described as the leader of the Valkyries, but this is misleading. The Valkyries choose the slain for Odin, whereas Freyja keeps her half of the slain in her own hall, Sessrumnir, in Folkvangr. The lore is tantalizingly spare in details regarding what Freyja does with her half of the slain, or why she chooses them. Jokes abound that those called to her hall no doubt enjoy themselves tremendously. Given Freyja's hedonistic tendencies, this is a fair assessment, but I doubt it's her primary purpose in keeping the slain in her hall. I believe she chooses her half for their cunning skills in defense to be used in protecting Asgard and Vanaheim during Ragnarok, leaving the fierce berzerkers for Odin's offensive front.
The lore tells us that Freyja survives Ragnarok, perhaps remaining behind to guide the next generation of gods in the process of rebuilding. Snorri Sturluson's assertion is that Ragnarok had already happened (he was, after all, writing for a Christian royal court), and Freyja was nevertheless still worshipped in his own day by some women. There seem to be at least remnants of folk traditions honoring Freyja in Sweden surviving today. Arguably the the Midsommerstangen, which is similar to a Maypole, but danced at the Summer Solstice, can be associated with the fertility traditions of the Vanir.
Freyja not only teaches magic - especially the Vanic art of Seidhr trance magic - it seems Freyja IS magic. In the experience of many in my local community, myself included, Freyja has repeatedly, through sepparate mediums, indicated an ability to sever the line of flowing wyrd that allows the gods to ride human mediums. She has threatened more than once to bring seidhr rituals to an abrupt halt if necessary, and may be one of the few gods with enough power or authority to pull Odin off of a human without his own cooperation, even if they belong to him outright.
Many people surmise that Gullveig is a kenning for Freyja. While this makes sense, it is not my experience. Gullveig is another of the Vanir, most famous for becoming a Heide (i.e. a witch) when the Aesir stabbed and burned her to death three times in a row in their hall, only to watch her rise again. The arts that Gullveig used are Vanic arts associated with Seidhr, and Freyja knows them at least as well - as do many of the Vanir, certainly including Freyr. Seidhr is an entire study in its own right, and anyone who wishes to undertake the study of Seidhr would do well to cultivate a working relationship with Freyja.
Most portraits of Freyja depict her with golden hair and porceline skin. My experience is much more varied. Perhaps to demonstrate that beauty comes in countless forms, Freyja appears in the widest variety of guises that I have ever perceived among the Northern gods. She generally appears fair-skinned to me, but her hair and eyes and clothing can vary across the full range of coloring found among the Northern people, and I would never put it past her to appear with darker skin if that was what best reached her audience.
* If you approach her as a goddess of love and beauty, you may associate her with the colors of gold and amber, with hints of warm reds. She may appear with warm eyes, and hair to match her amber and gold.
* As a goddess of fertility, she may come dressed more in greens and other earth tones. Her hair the color of flax, or sometimes the rich mahogany of good soil, her eyes often the green of spring shoots.
* If you seek the Seidhkona, expect darker colors - blacks and deep browns, some times with flecks of bright gold. Her hair may seem deep auburn, or even black at times, reflecting flashes of the fires on the brocken, her eyes unfathomably deep, almost dark.
* The chooser of the slain often comes in the bright crimson of freshly spilled blood, her hair pulled tightly back, out of her way, often bright copper red, or so blonde it's almost white.
* As Mardoll, daughter of the sea, and the mistress of the hawk, her hair is often wispy, very straight, the grey-brown color of hawk wings to match her cloak, and her eyes reflect the stormy blue of the Northern seas. She often seems very sad in this guise - I believe this is the form she took when mourning for Odr.
Regardless of her appearance, she is always breathtakingly beautiful. She is very much involved in introducing people to the ways of the Northern gods, and as such is often very forgiving of our modern foibles. If you wish to approach her, simply do so with an open, honest heart. Offer her what you can, and be sincere. Mead, amber, poetry, and chocolate are all good places to start. Simply sit and speak to her. Over time if you connect with her strongly, she may ask for specific things, and will expect you to educate yourself to the best of your ability, but Freyja has a very high tolerance for honest beginners, and will generally be very understanding that you are not already there. In this sense, I have also found Freyja to be quite willing to engage with Wiccans and Eclectic Pagans on their own terms (she is, after all, The Lady), at least initially. Freyja is a fierce goddess, but you need not fear her if you are being honest with yourself and her in your approach.
And Hail the Vanadis!