Last Thursday I attended a great presentation by Javier Peña, an introduction to Gerrit. In no particular order, this are the things that catched my eye:

Gerrit is a code review system. It sits between your source code repository (Git) and your developers, so any proposed change can be better discussed and reviewed. In parallel, Gerrit can be instructed to launch integration tests to ensure the proposed change doesn't break anything. If the CI integration tests are successfull, the patch can be merged with the code. Otherwise, further changes can be done by the submitter with git commit --amend until the patch is succesfully merged (or discarded).
It is better than Github's review workflow because:
- It's not propietary ;-)
- Can work in a disconnected fashion with Gertty
- Reviewing dozens of commits for a single PR can get confusing fast, specially with large patches.
- As mentioned earlier, Gerrit can be easily integrated with several CI systems.
Important opensource projects such as Openstack and oVirt are using it, although it started at Google.

There is project that is integrating Git, Gerrit, Zuul, Nodepool and a bunch of other tools to make development easier. It's called Software Factory and you can find additional info in their documentation: https://softwarefactory-project.io/docs/.

Happy hacking!