The "Edda" refers to two medieval Icelandic literary works, the Poetic Edda and the Prose Edda, which are the primary sources for Norse mythology. They contain myths, legends, and poetry about gods like Odin and Thor, and heroes such as Sigurd and Brynhildr. The Poetic Edda contains ancient poems, while the Prose Edda, written by Snorri Sturluson, is a textbook on Norse poetry and myth that retells these stories.