Each time you deploy an application to Deis, or change it's configuration, a new release is created and deployed.
You can review these releases using deis releases:
$ deis releases
=== <random>-<words> Releases
v4 3 minutes ago $USER deployed <sha1>
v3 1 hour 17 minutes ago $USER added DATABASE_HOST
v2 6 hours 2 minutes ago $USER deployed <sha1>
v1 6 hours 2 minutes ago $USER deployed $USER/repo
Rollbacks
You can rollback to any previous release using deis rollback. This will create a new release using the previous release:
$ deis rollback v2
Rolled back to v2
$ deis releases
=== <random>-<words> Releases
v5 Just now $USER rolled back to v2
v4 3 minutes ago $USER deployed <sha1>
v3 1 hour 17 minutes ago $USER added DATABASE_HOST
v2 6 hours 2 minutes ago $USER deployed <sha1>
v1 6 hours 2 minutes ago $USER deployed $USER/repo