Along with all the fun, creative stuff
it enables you to do,
programming sometimes requires you to carry out
boring and repetitive editing operations.
If those operations are uniformly applicable,
it's straightforward to automate them
using regular expressions
and a tool like sed,
or :%s/foo/bar/g in vim-speak.
But sometimes a regex can't express
the pattern you want to match against
and on those occasions,
vim macros can come to the rescue.