co-located branches (was: Pushing after merge)

[DeeJay]

   "I can suggest
<http://wiki.bazaar.canonical.com/MatthewFuller/AboutMainline>, which
    is neither concise nor exhaustive, but has helped one or two people get it."

@Matthew: thanks - not easy, for me, but helpful.

Now, could you perhaps do something similar for Colocated Branches? I don't seem
to 'get' those either.  :-(

[I've read http://doc.bazaar.canonical.com/bzr.dev/developers/colocated-branches.html,
but
still don't 'get' what they are or why I might want to use them.]

Thanks -

  DeeJay