In computer science, the general meaning of input is to provide or give something to the computer, in other words the state/act of a computer, component of a computer or relevant device being accepting something from the user, from a device or from a piece of software either automatically or manually is called input.
We categorize computer devices as input devices because we use these devices to send instructions to the computer, we are sending our "Input" to the computer, some common examples of computer input devices are:
We may also call some inner parts of the computer as input components to the other components, like the power-on button of a computer is an input component for the processor or the power supply, because it takes user input and sends it to other components for further processing.
In many computer languages the keyword "input" is used as a special keyword or function, such as in Visual Basic or Python, the word "input" is used to get text input from the user.