I really have no idea what 40k is about anymore!! (not a rant, I need pointers!)

What with me playing Infinity a lot recently, and not really having played a game of 40k since the GT40K tourny back in 2011 at Maelstrom Games, I have seriously lost track of the game. There have been so many releases of codexs etc in the last 3 years not to mention a whole new edition, I think I am literally back at square one. Just like back in 1990 when I first walked into a GW and the