The Poetic Edda (Codex Regius) is also named "Saemundr Edda" after an Icelander who was believed to have written it, though most historians agree that it was not Saemundr who wrote the Poetic Edda but a group of Icelandic historians.
During the 11th century a group of researchers began collecting folkstories and wrote them down to preserve them for future generations, this resulted in the Poetic Edda.
Many of those stories have been verbally handed over from generation to generation which has undoubtly changed many details though the main events of many stories have probably remained the same, one must also keep in mind that the Edda's were written down by Christian writers who misinterpreted or even adapted many facts, many people treat the Edda like some sort of bible but we must not forget that it's basically a collection of folk tales from a late period that can't match sources like for instance Tacitus' Germania, even though the Edda's are still a valuable source of course.
There is much debate about which stories belong in the Edda and which don't, this has resulted in several versions of the Poetic Edda in which the texts and sequence of them are not always the same.
To give you an impression of the contents of the Edda I have listed the texts (and brief contents of them) on this page, I used the texts and sequence of the Dutch translation by Marcel Otten since that is one of the most complete:
Völuspá ("the Vision of the Seeress"): in this story the god Odin visits a dead seeress to ask her questions about the future, she eventually tells him about the end of the world and that he will die in that last battle, this story contains much information about Germanic mythology.
Hávamál ("the Song of the High One"): this is the story of Odin in which he gives the reader advice and tells stories, a remarkable feature of this text is that Odin is very open about himself, personally I find this one of the most interesting texts of the Edda because it contains much wise advices that are still applicable today.
Vafþrúðnismál ("the Song of Strong Mangler"): In this text the god Odin holds a wisdom contest with the Giant Vafþrúðnir, who is the wisest being in the universe, their questions and answers give much information about Germanic mythology and eventually Odin wins when he asks Vafþrúðnir a question only he knows the answer to.
Grímnismál ("the Song of the Masked One"): this text also gives information about mythology and tells the story of two princes, it also lists some of the names of Odin.
För Skírnis ("the Journey of Glitter"): in this story the god Frey falls in love with a Frost Giantess named Gerd and he sends his servant Skírnir to pursue her to marry him, she refuses and eventually Skirnir has to threaten her to reach his goal.
Hárbarðslióð ("the Verse of Greybeard"): in this story the god Thor gets a quarrel with a ferryman called Greybeard who refuses to bring him to the other side of the river, some of the insults are hilarious (when properly translated that is).
Hymiskviða ("the Ballad of Hummer"): tells about the adventures of the god Thor and the Giant Hymir who go out fishing and catch the sea serpent Jörmungandr, Hymir fears the snake and eventually cuts him loose, giving it the chance to escape.
Lokasenna ("Loki's Insults"): in this story the god Loki disturbs the banquet of the sea god Ægir and insults the gods who are present at the party, this is one of the most funny texts of the Edda.
Þrymskviða ("the Ballad of Trouble"): the Giant Þrym has stolen Thor's hammer Mjöllnir and will only give it back if he is allowed to marry the godess Freya, Thor disguises himself as Freya in a wedding dress and goes to the wedding, he then throws off his dress, grabs his hammer, and kills all the Giants, this is one of the coolest stories of the Edda.
Baldrs draumar ("Baldr's Dreams"): the god Baldr is having nightmares about his own death and his father Odin travels to Helheim to ask for an explanation of this dreams.
Völundarkviða ("the Ballad of Völund"): the story of Völund the smith who is held hostage by a king, eventually he takes revenge by killing the king's sons and raping his daughter after which he escapes.
Rígsþula ("King's Register"): in this story the god Heimdall travels to Midgard disguised as Rigr, he visits three houses and divides humanity into three ranks; Thrall, Karl, and Jarl.
Alvíssmál ("the Song of Allwise"): in this story a Dwarf named Alvíss visits the god Thor and asks him to marry his daughter, Thor keeps the Dwarf busy with questions and when the sun comes up its rays turn the Dwarf to stone.
Grottasöngr ("the Grinding Song"): the song of two Giantesses who have to work for the evil king Frodi who forces them to make gold with his grinder, eventually they are fed up with the king and they grind an army that defeats him, after that the grinder sinks to the seabottom where it starts grinding salt into the water, this is how the sea turned salty.
Helgakviða Hundingsbana in fyrri ("the First Ballad of Helgi, the killer of Dog's son"): a text about the battle between Helgi and Hödbrod.
Helgakviða Hjörvarðssonar ("the Ballad of Helgi Hjörvarð's son"): this text contains two stories; one about Hjörvarð and one about his son Helgi.
Helgakviða Hundingsbana önnor ("the Second Ballad of Helgi, the killer of Dog's son"): the story of Helgi's life and death.
Frá dauða Sinfjötla ("About the Death of Sinfjötli"): this story tells about the death of Sinfjötli.
Grípisspá ("the Prediction of Grípir"): in this story the heroe Sigurð (Siegfried) visits a seer named Grípir and asks him about his future, Grípir eventually tells Sigurð about his own death.
Reginsmál ("the Song of Regin"): the story of the Dwarf Andvari (Alberich), how Fáfnir murders his father Hreidmar and takes the treasure of the Niflungar (Nibelungen) for himself, and Sigurð's revenge on the murderers of his father.
Fáfnismál ("the Song of Fáfnir"): Sigurð's victory over Fáfnir (who had changed into a dragon).
Sigrdrífumál ("the Song of Sigrdrífa"): Sigurð frees the Valkyrie Brynhild (Brünhilde) from her fire circle, the text also gives some information about runes.
Völsunga saga ("the Saga of the Völsungen"): the Otten translation only describes a small part of the actual Völsunga (Walsungen) saga, it tells the parts of the story with Sigurð in it.
Brot af Sigurðarkviðu ("Fragment of the Ballad of Sigurð"): the dishonourful murder on Sigurð (Siegfried) by Gunnar (Gunther) and Högni (Hagen).
Guðrúnarkviða in fyrsta ("the First Ballad of Guðrún"): the mourning of Sigurð's death.
Sigurðarkviða in skamma ("the Short Sigurð Ballad"): the rest of the Sigurð saga and the death of Brynhild.
Helreið Brynhildar ("Brynhild's Helride"): after her death Brynhild travels to Helheim and speaks with a Trollwoman.
Dráp Niflunga ("the Murder on the Mistlings"): the murder on the two Niflungar (Nibelungen) brothers Gunnar and Högni.
Guðrúnarkviða önnor ("the Second Ballad of Guðrún"): the attempts of Atli (Etzel) to marry Guðrún, Atli is the historical figure Attila the Hun.
Guðrúnarkviða in þriðja ("the Third Ballad of Guðrún"): Guðrún is being accused of adultery but proves to be innocent.
Oddrúnargrátr ("the Lamentation of Oddrún"): Oddrún complains about her life.
Atlakviða in Groenlenzka ("the Greenlandic Ballad of Atli"): a text about the invitation of Atli, the betrayal of the Huns, and the revenge of Guðrún.
Atlamál in Groenlenzku ("the Greenlandic Song of Atli"): this is a more detailed version of the Atlakviða in which Atli is murdered by Guðrún.
Guðrúnarhvöt ("how Guðrún Stirred Up her Sons"): Guðrún tells about her griefs and stirs up her sons, the story has a good chronology that lists the sometimes confusing events around Sigurð, Helgi, Atli, and others.
Hamðismál ("the Song of Hamðir"): the murder on the Ostrogothic king Jörmunrek (Ermanarik) and the battle with the Goths.
Hlöðskviða ("the Ballad of Hlöð"): this text tells of a great battle between the Goths and the Huns, it is not sure whether this has been an actual historical event.
