Your question is all over the place, but I'll throw out a few thoughts...
If you know what you're *supposed* to be doing, as far as a plan, you will realize that worrying about what each given piece can do is the wrong train of thought. For example, one plan might be to trade off your opponent's fianchettoed bishop at g7, and a common way to do that is to play Qd2 (to back up your bishop), Be3, then Bh6. Another plan would be to take advantage of a hole in your opponent's pawn structure, and a common way to do that is to post a knight at that square where the hole is. Another plan might be to exploit a pawnless f7-square, and a common way to do that is to aim your bishop at it via Bc4. Each plan has a typical way of carrying it out, whereupon selecting the right piece is already set for you.
i've asked a similar question so maybe i'll get a similar answer, but how do you know what each piece is capable of...meaning...i guess how do you know what move you are making is really effective and why? i can get around just guessing and going by with whatever the best moves are on here, but in a real live chess game i probably honestly wouldn't know what in the heckaroonies i'd be doing. i know, i know. i should read a book, but i honestly don't have money to buy one at the moment. this is one of the only ways i can really learn. maybe an answer for each piece and each move can't be given because the game is so variable, but i'm pretty sure everyone's making conscious moves right? no one's just making moves saying "alright whatever i'm bout to win this game".