Default What ROM am I running?

Hello first post here and i'm still a bit of an Android noob so here is a dumb question, I have just rooted my HTC One M8 using TheUnlockr All in One Kit method and my question is what ROM am I running? (I would link but new here) When you Root a phone does there have to be a custom ROM installed to have SuperSu on the phone, or is that all rooting is, just installing a custom recovery and installing SuperSu. For me the phone seems like it is just running the stock Sense ROM but I have been looking into flashing Cyanogen mod, and I want to know what I am currently using in case I want to get rid of Cyanogen. Sorry if this is confusing and stupid but yea. Thanks!