A computer is a machine that takes input, processes it, stores data, and produces output.
People often say computer when they only mean the screen, the operating system, or one app. That confusion makes every later lesson harder.
A computer is the whole machine: the physical parts plus the logic that lets it take instructions, remember information, and show results.
A computer is a smart machine that listens to instructions, remembers things, and helps you do work or play.
The computer is the whole system. It includes physical parts like the processor, memory, and storage, but it also depends on software to become useful.
Many people point at the screen and say "computer," while others mean Windows, Linux, or one program they use every day. Those are parts of the experience, but not the whole machine.
Study the larger concept after the word itself becomes clear.