Locks and then caches all of the gems into vendor/cache
$ bundle package [--no-prune]
--no-prune: Don't remove stale gems from the cache.
The package command will copy the .gem files for every gem in the bundle into the directory ./vendor/cache. If you then check that directory into your source control repository, others who check out your source will be able to install the bundle without having to download any additional gems.