most commonly used git commands?

I did this by mistake:

$git fet linux-2.6
git: 'fet' is not a git-command

The most commonly used git commands are:
   add     Add file contents to the changeset to be committed next
   apply   Apply a patch on a git index file and a working tree
(use 'git help -a' to get a list of all installed git commands)

why does git say that add and apply are most commonly used git commands?

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MST