Gerrit is

Advanced Git Interfaces: Gerrit >>> Gerrit is: >>> Using Git for Distributed Development

An enhanced method of using git for more complex projects

A more advanced replacement for git

Gerrit is built on top of git

============================

It introduces a more robust layer of code review by potentially mutliple individuals

This can really help to utilize more eyeballs and talent

It can reduce single maintainer bottlenecks

Sometimes an individual maintainer/reviewer cannot work fast enough for many reasons

============================

There is one change per commit

There are many changes to commit

This makes review easier

============================

The upstream and then reviewers pick from there

The reviewing layer, rather than fully upstream

Use of this layer is a major purpose of Gerrit

============================

Work only with the upstream layer

Work only with the contributor layer

Work with both the upstream and contributor layers

Reviewers work directly with contributors and decide when and how to submit upstream