A computer is a multipurpose digital device that can accept, process, manipulate and output data. A computer consists of hardware and software. Hardware is the name given to the physical components of the computer (e.g. the keyboard, mouse, motherboard, CPU etc). Software is the name given to the actual data that is being manipulated. Computers have many uses. For example they can be used to complete simple tasks like creating documents, browsing the web and playing games. But they can also be used for more complex tasks such as simulating nuclear weapons experiments and doing complex calculations. In the early days of computing, computers used to be extremely large and could take up entire rooms. But as time has gone on, they have decreased in size and could be even smaller in the future.
Sources:
https://edu.gcfglobal.org/en/computerbasics/what-is-a-computer/1/