Head
hg heads
A head is a ChangeSet with no children. The ["Tip"] is the most recently changed head. Other heads are recent ["Pull"]s into a ["Repository"] that have not yet been ["Merge"]d.
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 MultipleHeads concurrently within a single repository.