What are they called "candidates" for?
Why doesn't Carlsen play in the Candidates right now?

He qualified to play in the world championship match by winning last years same event. Now he's world champ & the winner of this tournament will challenge him. He doesn't have to keep playing in it as long as he's champ. The same applies to anyone who dethrones him, then they won't have to play in it either because they will be the new champ.

He doesn't have to; all current chess World Champions are automatically qualified to play for the chess World Championship match.

Did he have a bye in first round?
Heinzie, the posters are pulling your leg . The candidates tournament is so called because all of the participants are candidates to become the next world champion. The winner of the tournament goes on to play head to head against the current world champion,who as you know happens to be Carlsen.
Therefore Carlsen couldn't play in the candidates because if he won he would end up playing with himself and we wouldn't want to see that would we?

Carlsen is a good player but I don't think he can win a tournament like the Candidates.
Ooooooooookay.
Carlsen didn't qualify: he didn't lose the last championship, he didn't participate in the World Cup or Grand Prix, and the organizer didn't nominate him.

He got a bye for the first 14 rounds.
Hey! That's not fair! I mean, he's good, but he's not that much better than everyone else. I would say 3 or 4 rounds max.

I read someone's idea to get rid of the World Champ title and do something similar to pro tennis. You have a few top tournaments and the titles get spread around more. I like the idea, personally. If one player can dominate - fine. Magnus is the undisputed king. But as it is now the champion is in an easier position to defend his title - it's a little unfair considering how strong the best GM's are right now.
Did he have a bye in first round?