A long time ago, in a college far far away, some nerds were playing with UNIX. At that time, UNIX shipped with ed. Some rather clever programmers made a replacement for ed called em. Em became en. En became ex. Ex is Vi. Why is this important? Understanding where Vi comes from, helps you to understand its rationale. Why does Vi matter? It's an editor that has become part of the UNIX specification. Knowing Vi means that you know at least one text editor that is present on nearly all UNIX-like operating systems (ones like: most Linux distributions, *BSD, AIX, HPUX, Solaris, OSX, etc...). This makes Vi the defacto UNIX editor. Also, while it may take time to familiarize yourself with Vi, once you know it you can be insanely efficient.