Chrome releases a stable version each 6 weeks. So does Firefox now. But both of them have 2-3 other versions that are ahead of the stable one and go from dev to beta, or something like that. But those are not stable ones so you can disregard those. They also change every 6 weeks I believe.
So when Chrome 14 stable is out, Chrome 15 beta is out and also Chrome 16 Canary. Then in 6 more weeks, Chrome 15 stable will be out, Chrome 16 beta, and Chrome 17 Canary will also be out...and so on. They run in parallel. I believe Firefox has something similar.