This is the file that vi (or vim or elvis or whatever vi-clone you're using) reads in to customize your editting environment.
Two Everything 2-specific vi-macros I have are:
map ^x :w^M:!ispell %^M
map ^c ebi[^]ea]^[
The first calls up the spell checker and the second puts square brackets around the current word.
The safest keys to use for vi command mode macros are:
K, V, g, q, v, ^a, ^c, ^i, ^k, ^o, ^q, ^s, ^v, ^w, ^x, ^z
because they aren't normally used. Note how clever it is that most of the free control keys are all clustered on the left side of the keyboard.