Need Help Understanding Trades

Greetings Chess.com community!  I've been trying to improve my game using the study plans and Chess Mentor.  However, I'm having a hard time understanding when to trade pieces. I posted a computer analyzed game, against a friend I frequently play, and get confused when it shows the better move as an exchange or sacrifice.  Any advice would be greatly appreciated.  Thank you!

Hi WarBird. You've asked specifically about 6. d5, but based on the game you posted, my advice would be to go back over your moves and focus on the ones marked Blunder. For instance look at 14. Bg5. Were you aware when you made that move that Black can capture either of your knights?

Basically you made a move that lost you a piece. I would work first on consistently getting through games without making clear mistakes such as that one. Then you'll have a better foundation for considering your good question above.

I'm really starting to dislike looking at the analysis that computers give people. Computers aren't intelligent enough to give good positional analysis, from what I've seen. Many people here are advising to ignore computer analysis, and I agree, unless it's something clear-cut, like a mate-in-x.

5. Bxe6: I'm not sure about this. After 5...fxe6 it gives Black one advantage of a pawn at e6 that can nicely support the pawn push ...d5. On the other hand, it removes Black's only good bishop.

I'm not sure about 7...Nxc6, either. One the positive side it develops a new piece instead of moving the bishop multiple times in the opening, but on the negative side it will be harder for Black to play ...d5 with a knight there instead of a bishop.

I don't see 12. Nb5 as a "blunder." 12...Qa5+ doesn't fork the knight because the knight can just retreat back to c3. However, it was certainly a wasted move, which you could have guessed since it moved the same piece twice in the opening.

That software sure overuses the word "blunder." I don't use that term unless the move clearly loses the game. You did make a lot of mistakes, but most of them were positional, not "blunders." What I would do if I were either side is to study Philidor's Defense better so that I knew where pieces were typically placed in that opening, especially Black's QB. I believe it normally goes to g4, but I also know that it's considered a mistake to play ...Bg4 too early.

All of which is a fancy way of saying "I don't know." You post did motivate me to study the Philidor more, though.

(Please allow 15 minutes after this post for me to correct my inevitable errors.)

There is a chess mentor course on this topic

http://www.chess.com/chessmentor/view_course?id=201

Thank you for the advice! I'll make it a goal to get through my games without making mistakes, I'm defiantly going to dive into the Philidor defense, and thank you for the link to the chess mentor lesson. I'm excited to study it.