what does this move achieve? I was watching the current Carlsen vs Adhiban game and I saw a move that always puzzles me:

5. h3 Bh5


I'd say Carlsen want to unpin the knight, or kick the bishop away. The bishop retreats, while keeping pressure on the same diagonal

6. Be2


This move I don't get. I can imagine that 6.g4 would cause positional trouble on the kingside, so the bishop is moved to e2 in order to break the pin.

But if this is true, then why did Carlsen play 5.h3 in the first place ? 

I don't get what does 5.h3 achieve.

Thanks !
I see at least 3 good points to 5. h3:


first and foremost, it puts a question to the Bishop: if Black wants to maintain the pin, he will have to move it to h5, which is more vulnerable and decentralized. Moreover, once the Bishop will be on h5, white squares on the Queenside will become vulnerable, as the Bishop cannot retreat and defend them in one move (just have a look to b7, for example);
once the Bishop is on h5, White can kick it away with g4 if he wants, gaining space and advancing a Pawn with tempo;
now that h3 is in place, h2 becomes a comfortable flight square for the King if White castles Kingside, thus avoiding first rank weaknesses during the endgame.