A computer is a machine that processes data based on a set of instructions provided by software. It has components like a CPU, hard drive, RAM, and monitor. Software includes programs for games, documents, and multimedia. Operating systems run basic computer operations and come pre-installed on purchased computers like Windows, Mac OS, and Linux. Computers are turned on by pressing the power button and turned off through the start menu or keyboard shortcut. Mice are used by left clicking to select and right clicking for shortcuts.