The first fact would be concerning the opening, which is a traditional appeal to a Muse in order to give the author inspiration to be able to tell his tale. Other epic texts begin in a similar way, with the author appealing to divine inspiration to help him narrate the tale. This is why the story begins in this fashion:
Tell me, O muse, of that ingenious hero who travelled far and wide after he had sacked the famous town of Troy.
A second fact would be that Odysseus, the "ingenious hero" in the passage, was a character who was very much involved in the siege of Troy, which Homer wrote about in his other major epic, the Iliad. It was only after the sacking of Troy and the end of the battle that he was able to think about going back home to Ithaca and to his wife, Penelope. Lastly, it was Odysseus who came up with the idea that successfully resulted in victory for Agamemnon's forces, as he was the person who thought up the cunning plan of the Trojan Horse, which allowed the Greeks to place a small group of men within the city who could then open the gates and allow the Greek army to enter the city and sack it. The three facts to the opening of this tale therefore relate to its style and also its heroic figure, Odysseus, and his exploits before the tale starts.