Events are user interactions with their computer, such as a mouse click or key press.
In the good ol’ days, computers handled user interactions as input of batched data. The user fed a hunk of data in, the computer did something to that data, then produced the results. With the advent of interactive devices like the GUI interface, computers could display answers to computations onscreen. The input for these interactions are events caused by the user, which could be keystrokes, button clicks, or the position of the mouse pointer. (see Event Handler).