"COMBIN" is useful for when you want to (for example)quickly calculate how many lines your entry needs when doing the football pools. So if you have selected 12 draws and want to "perm" any 8 from 12, the formula is "=COMBIN(12,8)" which gives you 495. The pools companies and the bookmakers erroneously call this a permutation. Try "=PERMUT(12,8)" and you'll find this to be a much higher figure.
Agree with you 100% about learning through browsing this site.