+``git reset`` moves the head of the current branch. The head can be
+moved to point to any commit but it's often used to remove a commit or
+a few (preferably, non-pushed ones) from the top of the branch - that
+is, to move the branch backward in order to undo a few (non-pushed)
+commits.
+
+``git reset`` has three modes of operation - soft, hard and mixed.
+Default is mixed. ProGit `explains
+<https://git-scm.com/book/en/Git-Tools-Reset-Demystified>`_ the
+difference very clearly. Bare repositories don't have indices or
+working trees so in a bare repo only soft reset is possible.
+
+Mixed mode reset with a path or paths can be used to unstage changes -
+that is, to remove from index changes added with ``git add`` for
+committing. See `The Book
+<https://git-scm.com/book/en/Git-Basics-Undoing-Things>`_ for details
+about unstaging and other undo tricks.
+
+TODO: describe undo strategies: git reflog, git revert.