Later is a way to talk about time: some time after now. You can go to a movie later tonight.
Later can also mean more recent, as in "Which is the later movie, Gone with the Wind or Citizen Kane?" It can mean toward the end: “He made that movie later in his career.” It can also mean after, as in "You were later than I thought you'd be!" It can also be used in comparison: "He was late; I was later." All these uses are about time, and how time keeps moving on from now to later.