Clone
hg clone [OPTION]... SOURCE [DEST]
To clone a repository is to make a copy of it at a point in time. The new repository is self-contained.
A cloned repository is not a branch.
Clone checks out the tip of the default (aka unnamed) branch (see NamedBranches). Ergo, you probably want to keep your main branch unnamed.1
Help text: http://www.selenic.com/mercurial/hg.1.html#clone
See also: TutorialClone, CommunicatingChanges, Pull, WorkingPractices, RepoSamples, HardlinkedClones