Short answers, pulled from the story.
The Tale of Ragnarr Loðbrók is a 13th-century Icelandic legendary saga about the Viking warrior Ragnarr loðbrók, a Danish king's son. It covers his killing of a serpent to win his first wife Þóra, his later marriage to Áslaug, the battles of his sons, and his death in King Ælla of Northumbria's snake pit.
Loðbrók means "hairy trousers" in Old Norse. Ragnarr earned the name by wearing wolfskin trousers boiled in pitch when he killed the serpent guarding Þóra borgarhjǫrtr, and the saga treats the garment as the origin of his nickname.
Áslaug was the daughter of the legendary hero Sigurðr Fáfnisbani and the Valkyrie Brynhildr. She lived in hiding under the name Kráka at a farm called á Spangareiði, became Ragnarr's concubine and later his wife, and bore him four sons: Ivarr beinlauss, Bjǫrn járnsíði, Hvítserkr, and Sigurðr Ormr í auga.
Ragnarr is captured by King Ælla of Northumbria during a war march and killed in Ælla's snake pit. Before dying, he recites the poem Krákumál, invoking his sons, who later avenge his death.
Krákumál is a poem that Ragnarr sings while dying in King Ælla's snake pit. In it, he recounts his deeds and calls upon his sons. The poem is named after Kráka, the alias Áslaug used while living in hiding.
Ragnars saga loðbrókar appears immediately after the Vǫlsunga saga in the earliest known manuscript, functioning as a sequel. Through Áslaug's parentage as the daughter of Sigurðr and Brynhildr, the saga draws a line from the legendary figures of the Vǫlsunga saga to the historical events of the 9th to 11th centuries.