Airbrake collects errors created by WordPress and it's plugins.
An exception happens when part of your WordPress site crashes. On its own, WordPress is not setup to deal with errors gracefully. This means you get an ugly error message that makes it difficult to determine what exactly went wrong.
Plugins can often cause parts of your WordPress site to crash and stall. This plugin lets you quickly identify broken plugins, and send that information to your developers (or handle it yourself) FAST.