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.
The following lines lines in Book One are from Lattimore's translation of the Odyssey.
"Tell me, Muse, of the man of many ways, who was driven
far journeys, after he had sacked Troy's sacred citadel.
Many were they whose cities he saw, whose minds he learned of,
Many the pains he suffered in his spirit on the wide sea,
struggling for his own life and the homecoming of his companions
Even so he could not save his companions, hard though
he strove to; they were destroyed by their own wild recklessness. . .
From some point here Goddess, daughter of Zeus, speak, and begin our story"
Within this short introduction of the Odyssey, three of the most important themes within the epic poem are revealed to the audience. The first is that of metis. This is a Greek word meaning cunning and intelligence. It is only because of Odysseus' cunning that he is able to return to Ithaca. He is no different from his crew in that he is also reckless. He shouts out his real name to the cyclops, Polyphemus, who then asks his father Posiedon to inhibit Odysseus from returning home. However, he is different from his men in that he possesses a superior intelligence. This metis is greatly admire by the goddess Athena. Without her help and his cunning Odysseus would not be able to return home.
This introduces the next theme: Nostos. This is the Greek word meaning homecoming. The Odyssey is the story of Odysseus' journey to return to his home, Ithaca. The epic examines the disconnect created by war and how true victory is only fully attained once the hero returns to his home. However, it also appears that one never can truly return "home." As Odysseus discovers upon arriving in Ithaca, his native land will never be the same place that it was when he left for Troy.
The final theme is that of powerful women throughout the Odyssey who like Odysseus possess a superior metis and are essential in his return to Ithaca as King. Because Athena has pity on Odysseus and admires his intelligence, a genius she also possesses, Poseidon can no longer forever delay his return. Similarly women such as his mother(underworld) and the Phoenician queen, who weaves (a symbol of intelligence), aid him in his journey. Penelope also weaves as a sign of her metis. It is Penelope's loyalty that allows Odysseus to return as the king of his household.