Why do i have a slight advantage in this position?

en.lichess.org/ImEvfZ43

is it because of the pressure my pawns are putting white under and that the knight is a more active piece than the rook?

White is more active..

White has just sacrificed 2 pieces for a rook and 2 pawns. There are no open files in a position so far (no use for extra rook yet), and white doesn't threaten blacks king, and there are no other weaknesses really. In an endgame this material difference is most often good enough for white to ensure winning chances or at least draw, but in the early/mid game having an extra piece for black often creates opportunities to win material back, thus giving better game to a side with more pieces (black here).

@kekmeme #1
Two light pieces (bishop or knight) versus a rook is a material imbalance which is not so easy to understand right away when learning chess.

When the position is semi closed or closed, the party with the 2 light pieces might have an advantage.
When the position is open and not many pawns left on the board, the rook can excel, and in some cases the two light pieces can get in trouble.

In your game white is however getting 2 pawns + rook for bishop and knight. The position is closed, and white's center and kingside pawns will probably soon start rolling.

Stockfish probably looks mainly at material difference in the end position. rook + 2 pawns = 7 versus bishop + knight = 6

I would slightly prefer to play white here, centralize the white rooks and get the pawns rolling. Black will have to play carefully.

But you should indeed have played on though !

@kekmeme Just to counter @achja - I'd take Black here...

White might manage to exchange some pieces off and win the ending, but I suspect the next few moves are going to be much more fun for Black, re-arranging his pieces, breaking with d5 and attacking along the open diagonals - definitely a finely-balanced position.

I've knocked a few moves together into a study, which doesn't change my evaluation.

en.lichess.org/study/icLF7EDa

I think I'd prefer black here. The main reason is that in this position white's basic idea is to create a pawn steamroller, but the specifics of the position don't work for that. In particular white's e4 is a really annoying weakness that makes it very difficult for white to get his pawns moving, and can also help black undermine white's center with moves like c4 eventually. If we do something as little as change that e2 knight to a light bishop I'd think white would have a fairly sizable advantage. But as is e4 is just so annoying.