Note: checkouts are a work in progress and do not exist in bazaar-ng yet
A checkout is essentially a [:WorkingTree:] with a relatively small amount of metadata. The meta-data is primarily there to point at the branch that the checkout is associated with.
Checkouts provide a location for people to hack on code and commit. Once a user [:Commit:commit]s, the associated [:Branch:branch] is updated with a new [:Revision:revision] that represents the changes for the commit.