A while ago I knew absolutely nothing about cisco IOS naming. I will admit, now I only know a little bit more than I did before but it's still better than nothing.
This pdf goes through some of the basics about the different feature trains that cisco has and uses. Though it's still fairly confusing its a good resource to get fairly familiar with the naming and what everything means.
Cisco Naming Convention PDF
Another amazing resource for finding what IOS you may need if you don't fully understand the naming conventions is Cisco's Feature Navigator. It easily allows you to find the IOS you need for the features you want, as well as compare other IOS features to the one you may currently have or want to use.