Which Grip is it?

What is the difference between the much talked about Twisted Grip and Split Grip (Regular)? When I'm looking at someone doing it all I see it that in both grips thumb is up (as opposed to the Split Grip (True) where pink is on top). I am really using these grips just yet, but when I see someone doing moves I have trouble deciphering which grip they are using. What should I be looking for? Sorry if this sounds ridiculous or makes zero sense. :)