I don't understand some of the best moves on key moments

Some best moves doesn't make sense to me. Like why do I will open up a way for the opponents rook to develop, why takes a pawn that being depended by 3 pieces and will lose 4 piece and gain disadvantage? I am noob but please someone explain what to look for on those key moments best moves suggestions.

Sorry for my grammar I am Asian

Understanding the best move evaluations requires following the variations shown and the resulting positions.

Is there some position in particular that confused you?

I really forgot what moves but every game I review then they show best move that makes me wonder why? I think I really need to learn more to figure it out

Sometimes engine moves are very hard to understand. It always depends on the concrete position, there is no miracle abstract rule that will always help you. If you want answers, post games.

If you post a game and explain some of the moves it says were best that you don't understand someone might be able to better explain why it is good. I also find that if you pull up the analysis board and try the moves you think were good. It often will show why I was wrong and why the move they suggested was best. 

Improving Your Chess - Resources for Beginners and Beyond...

https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond

Hi

I don't understand some move too, above all the best moves, sometimes I can't see the key moments. I feel I can't improve :c

At our complete beginner level, understanding engine analysis could be very hard, almost impossible. Try and play through a few moves of a given variation, if you don't understand it, leave it and look at some other good moves in suggested lines to see if you can understand the point behind it. Spend very little time on it, or better yet, only use analysis to show you your blunders and big mistakes, that you can understand, and try to remember those.

Your time is better spent on trying to practise avoiding blunders, spotting opponents blunders, taking free pieces etc. Learn about opening principles, try to apply them and practise solving tactical puzzles

It's very hard to understand the analysis at any level, because even in the resulting variation the computer will play the best move for both players.

e.g. hypothetical: "a given variation is best for white because black was threatening a skewer next move but by threatening the rook with Nb6! white deflects a key defender because black himself could be forked next move, therefore making the skewer impossible and taking additional space to boot". But this understanding is hard to see from the computer variation, because 1. no skewer happens, 2. no fork happens, and 3. both players are making new plans with the rest of their moves in the variation.

There's not much to say for this, apart from you just need to take your time with these variations; don't expect to see the tactical motifs at a glance, and don't expect to necessarily understand all variations (I don't). Hopefully chess.com can make the analyses more descriptive in future, although I understand how challenging that task is.

As the advances in AI progress, e.g. see Maia chess, engine will be able to understand human style play more, and will be able to comment on those lines with explanations involving imperfect human play, would be great anyway😃

Unfortunately, there is no way to help you without some specific games to discuss. Post some games and show us where the engine analysis confuses you. Everyone will try to help