In layman’s terms this is a fancy way of talking about events that your computer’s CPU performs. Each event, which can be triggered by a pulse from the clock, can be considered a cycle. Or, as if often the case, the CPU has a series of little routines it is constantly running. Things like: check each I/O port for incoming data (keyboard, mouse, modem, etc.), update the screen, move data from here to there, etc. Basically a series of events that are required to keep the computer operating. The computer keeps repeating them over and over. A cycle can be considered to be one pass through all of these events.