Chrome is available in four builds: the Stable channel is the main public client, the Beta channel has a few bugs but gets new features roughly a month before the Stable build, and the Dev channel is for developers looking to test out the latest features. Then there's the Canary channel, an untested build that gets updated every weekday with the latest codebase as soon as it's built.
The Canary channel was limited to desktop versions of Chrome on Windows and Mac, but is now making its way to Android. Considering the nature of the build, the Canary channel uses a separate profile and can be installed alongside the stable build.
From the Chromium blog:
Just like the Canary channel for other platforms, new versions are built from the most recent code available and often contain a variety of new features, enhancements, and bug fixes. These builds are shipped automatically with no manual testing, which means that the build can be unstable and may even stop working entirely for days at a time. However, the goal is for Canary to remain usable at all times, and the Chrome team prioritizes fixing major issues as quickly as possible.
Initially, builds will ship every weekday. In the future new builds may also be available on weekends. The frequency of builds means that keeping the app updated will consume a lot of data, typically more than 100MB per week. This is especially important for phones set to update native apps over cellular data.
Right now, there isn't a whole lot to differentiate the Canary build from the Dev channel, but in the future, new updates will show up on the Canary release before making their way to other builds. If you're interested in trying out the Canary channel, you can now install it from the Play Store.