The Warhammer license is spread across numerous franchises, and it is quite likely that you could be a huge fan of the brand, but not get the nuances of every game released within the universe. Developer Creative Assembly feels your confusion and has offered up a video for newbs who may not have ever played any of their Total War games.

Total War games mixed a turn-based component on the campaign map with a real-time mode as you choose you battles from the campaign. Heroes add an extra layer of play on both the campaign map and in the actual battles. Check out the video for a rather succinct overview: 

Total War: Warhammer hits for PC on May 24. If you want to play, be sure to get the game within the first week of release so you can add the Chaos Warriors pack for free.