Odysseus lies and tells Polyphemus (the cyclops) that his boat was shipwrecked off the coast of his island. He does this because he knows that Polyphemus will destroy his boat if he thinks it is sitting out there. That way, as soon as they can leave his cave, they will board their ship with his ewes and cheese. This shows how cunning and brave Odysseus' character truly is.
In Book 9 of the Odyssey, Odysseus tells the Cyclops that Poseidon, who is the Cyclops's father, "smashed my ship/he drove it against the rocks at your island's far cape" (lines 319-320). Part of the reason that Odysseus lies to the Cyclops is that the holds of his ship are filled with provisions that his men took from the Cicones' holy city, including "generous store in jars" (line 183). Odysseus wants to protect his stores from the Cyclops. In addition, Odysseus wants to be able to escape from the Cyclops's lair. At the end of Book 9, Odysseus slaughters the Cyclops's sheep and leaves with his remaining men on their ships, and the ships are critical to the survival of the men who the Cyclops has not killed. Odysseus blinds the Cyclops in order to escape, and Poseidon, the Cyclops's father and god of the sea, makes it difficult for Odysseus to return home in his boat.
Odysseus arrives at an expansive island which is home to the Cyclops. He takes twelve of his men to explore the vast lands, ending up at the cave of Polyphemus, one of the Cyclops. While Polyphemus is out grazing his giant sheep Odysseus and his party enter the cave and eat some of the food that was there, which included some meat and cheese. Polyphemus arrives back home to his cave and brings his sheep in and rolls a huge boulder to cover the entrance to the cave. Odysseus engages Polyphemus in a conversation hoping to secure hospitality but this idea is rejected. Polyphemus asks where they landed their ship, but because Odysseus knows that Polyphemus would just destroy the ship he lies and says they were shipwrecked by Poseidon. Finally Odysseus manages to escape but without some of his men who were eaten by Polyphemus.