Kinda hard to sum it briefly, as OS X has been going for almost 20 years now. 10.0-10.2 were fairly primitive operating systems, pretty much a beta. OS X started getting sophisticated around 10.3, when a more complete finder interface was added and overall system stability improved. 10.5 brought on a more 3d glassy look, and introduced features such as spaces and a reworked Finder. 10.6 was a stability release, improving on 10.5, and not really adding any new features. 10.6 was notable for cutting of PowerPC Macs. 10.7 introduced a new spaces design, as well as some UI redesigns with different button icons, and smaller traffic lights. 10.7 is where more iOS features begin showing up in OS X, such as launchpad and multitouch gestures. 10.8 was another stability release, the most notable new feature being the addition of iMessage. 10.9 was the first free version of OSX, and was a minor upgrade from 10.8, introducing more iOS and iCloud integration. 10.10 introduced a UI overhaul, changing the 3d look of OSX to the flat look if iOS, and introducing even more integration with iOS devices. 10.11 was another stability release, running much smoother than they buggy 10.10. 10.12 introduced Siri and a few other minor features, and renamed OSX to macOS. 10.13 is touted as another stability release, but is one of the buggiest versions of macOS to date, introducing a few more minor features in spotlight, and a new drive format that is much faster on SSDs than the previous standard.
As for better or worse, 10.6 is often touted as the most stable and best release of OS X, although software support for it is pretty nonexistent at this point. Since about 10.9, Apple has started locking down OS X, removing more "techie" features, and giving it more of the locked down feel of iOS, which I don't think is a good thing. If you are looking to choose an OS for a fairly modern Mac, choose Sierra. It's the most stable release that is supported at the moment imo.
Hopefully that gives you a basic idea!