A word processor is a computer Computer

A computer is a machine [i] for manipulating data [i] according to a list of instructions [i] ... 

 application Application software

Application software is a defined subclass of computer software [i] that employs the capabilities of a c ... 

 used for the production of any sort of printable material.
A word processor may also refer to a stand-alone computer unit similar to a typewriter Typewriter

A typewriter is a mechanical [i], electromechanical [i], or electronic [i] device wi ... 

, but often including technological advancements such as a screen, advanced formatting and printing options, and the ability to save documents onto memory cards or diskettes.