Who was Freya?
Freya wearing her necklace (about 800 AD)
Freya is the only important goddess of the Germans. She was married to Odin, and she's a kind of fertility goddess like Hera or Aphrodite or Venus. Her name just means "lady" in old Norse and old German. Friday is named after her, because in Latin Friday was Venus' day (Vendredi in modern French), and Freya was like Venus. Sometimes Freya seems to have been another name for the goddess Fricka, but in the story of the Niebelungenlied they are certainly two different goddesses.
Freya was also a goddess of magic, and she had a lot of magic stuff, like a cloak of robin feathers that let her change into any bird she wanted. She got the famous necklace called Brisingamen in exchange for spending a night with each of four dwarves.
Learn by doing: draw Freya's feather cloak and necklace
More about Odin
Bibliography and further reading about the Norse gods: