Chrome Canary is a frequently-updated experimental build of Google's flagship browser, that gets the latest changes before any other version.
Sounds good? Well, maybe, but there are problems. In particular, Canary's rapid updates come at the expense of manual testing, and so you may be trying out some new tweak that no human being has ever checked to confirm that it works. Sometimes this may work well, but even Google describe Canary as "a highly unstable browser that will often break completely", so there are clearly no guarantees.
Still, you can install Canary to run alongside the regular version of Chrome, so there's no need to choose between the two. You can easily run Canary for general, ad-hoc browsing, turning to Chrome when you need to carry out important tasks, like online banking, or if Canary just seems too unreliable.
There's no need to worry about manual updates, either, as Canary will automatically update itself daily (well, more or less). And so if you're a Chrome fan, or would just like to see where the browser is going next, then the program could well be worth a look.
Use with caution.
An interesting, if sometimes very unreliable look at upcoming Google Chrome technology