Head

hg heads [-r REV] [REV]...

A head is a changeset with no child changesets. The tip is the most recently changed head. Other heads are recent pulls into a repository that have not yet been merged.

If you have just made a commit, that commit will be the tip. Alternately, if you have just pulled from another repository, the tip of that repository becomes the current tip.

Mercurial supports multiple heads concurrently within a single repository.

Help text: http://www.selenic.com/mercurial/hg.1.html#heads