For each move, the Game Review includes an option to show what the result of your move is (e.g. why a blunder loses material or why a brilliant move is winning) by showing a sequence of moves that would be played under best play. So when you are confused about how Chess.com is predicting how the opponent will move, it is just giving you the best engine moves for your opponent.
When you're still less experienced with chess, try not to get overwhelmed by different explanations or moves that don't make sense; as you improve, you will start to understand why some moves are not very good or just learn to avoid playing them at all.
(Gaining a tempo is used to describe a move that improves your positional structure while at the same time as threatening the opponent in some way, so after they need to respond to the threat in some way, you can improve your position again while the opponent was busy taking care of the threat.
Before you flame me I did look for a an answered question on this.
I'm completely confused by both the numerical move rating system and and the overall word-based assessment. In particular, I often find myself saying the following things during replays:
"That move gave me +13, but I lost a major piece/the game in the next move? What?"
"WHY is that move a blunder?"
"Wait, I was losing the whole game? How?"
"How TF is this thing predicting how the opponent will move for five moves? There's no way to know that."
Sometimes there are explanations but they don't mean anything to me, like, "you gave your opponent a free pawn" or something, which may or may not actually happen or if it does it's like three of four moves later.
I've been playing this casually since I was a kid, but I've honestly never heard of half the terminology and when I do look it up it doesn't make any sense ("Gain a tempo?" what? That's like saying "gain a speed").