What is Rollback
Reverting a live system to the previous working version, usually within minutes. The standard first response to a bad deploy.
In plain terms
When a fresh deploy causes an incident, the fastest fix is going back to the version that worked. A hotfix is the alternative: a minimal emergency patch pushed forward. A revert can also target a single change, undoing one merged commit while everything else stays.
What it tells you about a developer
Developers whose merged work rarely needs reverting produce changes that hold up in production. A low revert rate on substantial changes is one of the cleaner reads of engineering judgment on a public profile.