1. Any information or data that's entered or sent to the computer to be processed is considered input. Input or user input is most often sent to the computer using an input device such as a keyboard or mouse. The picture is an example of input being sent from the computer keyboard to the computer.
2. In general, input can also refer to a contribution of feedback, information, or work. For example, someone may ask you for your input about a project they are doing at work or school.