Vi vs Vim vs gVim vs Neovim

TL;DR

• VIM = Vi IMproved. Vim is the editor that runs in a terminal shell — it has no GUI of its own.
• gVim is the vim editor with its own GUI.
• Neovim is a fork of Vim with additional features. It shares the same confg syntax with Vim.

Check detailed differences between vi and vim

Use builtin help:

:help vi-differences

Your vi may be linked to vim:

To check:

$ which vi
/usr/bin/vi

$ ls -l `which vi`
... /usr/bin/vi -> vim

Vi / Vim compatibility

Use -N or set​ nocompatible: Not fully Vi compatible, i.e. load vim features.