Vim (/vɪm/ ; short for vi improved) is a free and open-source text editor. Vim provides both a terminal screen user interface as well as a graphical user interface (called gvim).
Vim's documentation describes it as an improved form of the older vi text editor (though it is built from a distinct codebase). In release information, the author originally implied that Vim was an abbreviation for "Vi IMitation", but later, the expansion was changed to "Vi IMproved" because, as described by the author, the functionality had increased beyond that of a clone of vi. Some sources indicate the change happened with v2.0, but conflicting information (including from author) suggests the change happened as early as v2.0 and as late as v3.0.