So, Magnus won't defend the title?!

Yes. You read correctly: The current world champion Magnus Carlsen won't defend his title in the upcoming world championship. Although it was speculated that he would demand some changes for the format of the WC from FIDE, these negotiations however seem to have been about his reason for abdicating: Magnus just isn't motivated enough to play. Does this mean he'll retire from chess entirely? No, he made it pretty clear that he is still interested in chess - and according to him, he will still be an active player and has the goal of reaching a rating of 2900.

So, what will happen with the championship if the champion isn't around? Well, the winner of the last candidates tournament as well as the runner up will play: This means that Ian Nepomniachtchi will play against Ding Liren. With that, a change of world champions is guaranteed: The new champion will either be Nepo or Ding. We'll have to wait and see what will happen though.

What do I think about this all? Well, I can understand that Magnus feels unmotivated and even burnt out: Afterall, he's been the best player in the world for a decade now! Though I've gotta admit that I thought that he would change his mind and play, to get somewhat of a streak on world championships - like Kasparov did before him. I have a lot of sympathy for Fabi, who was the second in the two horse race that was the last candidates tourney. I also have compassion for Hikaru, who was the runner up up to the last game, though he probably doesn't care - even so, who knows if Magnus would have declined the match if he was second? Anyways, there ain't much we can do other than enjoy the game and hope for an interesting match.

Source: https://new.chess24.com/wall/news/magnus-carlsen-will-not-defend-his-title