Gerrit is firstly a staging area where changes can be checked over before becoming a part of the code base. It is also an enabler for this review process, capturing notes and comments about the changes to enable discussion of the change. This is particularly useful with distributed teams where this conversation can’t happen face to face. Even with a co-located team having a review tool as an option is beneficial because reviews can be done at a time that is convenient for the reviewer. This allows the developer to create the review and explain the change while it is fresh in their mind. Without such a tool they either need to interrupt someone to review the code or switch context to explain the change when they’ve already moved on to the next task.