The poems are all alliterative and use kennings. Authorship is impossible to determine, as well as original composition date for most. They were likely orally transmitted over generations before being committed to written form. Dating of a few can be done by internal information. One poem's title, for instance, Atlamál in grǿnlenzku ("The Greenlandic Lay of Atli") could not have been composed before 985, since Greenland had not been settled before that year. Occasionally a poem will mention an actual historical person, indicating the poem's composition obviously later than that person's life.
Another way of dating and locating the poems is by considering the flora and fauna mentioned. If a story contains wolves, for example, it could not have taken place in Iceland. There is always the chance, however, that poetic license was used to enhance a story.
The best-known and most-examined story in the Edda is the Vǫluspá ("Prophecy of the seeress") in which a seeress tells Odin the story of the creation of the world, its coming end, and its rebirth. It exists not only here, but also in another manuscript, and parts are quoted in the Prose Edda. Although dated to the 10th century, prior to the Christianization of Iceland, some think the idea of rebirth after destruction was influenced by Christian ideas of redemption and Heaven.
Speaking of Norse culture, Christianity, literature, and the Eddas, I hope you'll indulge me in discussing their influence on a 20th century Roman Catholic writer and medievalist named Tolkien; but that's for tomorrow.