Short answers, pulled from the story.
The Minotaur was a hybrid creature with the head and tail of a bull and the body of a man, born from the union of Pasiphaë and a snow-white bull sent by Poseidon. This unnatural birth resulted in a being named Asterion who required human flesh to survive.
The Minotaur dwelt in the center of a massive maze constructed by the architect Daedalus on the island of Crete. The palace at Knossos contains over 1300 maze-like compartments that some scholars believe may be the real-world inspiration for the Labyrinth.
Athens was compelled to send seven young men and seven young women to be devoured by the Minotaur every seven or nine years as retribution for the death of King Minos's son Androgeus. This cycle of violence continued until the Athenian prince Theseus volunteered to end the tribute.
Theseus received a ball of thread known as a clew from Ariadne to navigate the complex corridors and retrace his path to safety. He then confronted the Minotaur and killed the beast with a sword, a club, or his bare hands before leading the surviving Athenians out of the maze.
King Aegeus watched the black-sailed ship approach from the cliffs of Cape Sounion and presumed his son dead, so he leaped into the sea that now bears his name. This tragic event secured the throne for Theseus but cost Aegeus his own life and the life of his wife.
Modern works like Jorge Luis Borges's The House of Asterion portray the Minotaur as a lonely, sympathetic figure rather than a mindless killer. The creature appears as a playable character in role-playing games like Dungeons & Dragons and as a boss in video games like Assassin's Creed Odyssey and Hades.