I think I know what the guy is describing chess wise, but he explains it terribly. Pawns don’t retreat on the board, they only advance with the exception of en-passant where they can diagonally take another pawn passing them on their sides 4th row.
the sacrifice of rooks and bishops is probably actually straight trades, clearing the board. At high level going down 1 or 2 major pieces is a serious disadvantage, you don’t do that unless the opponent is playing to your strategy AND has few if any options to open up an offense. Any move that doesn’t force him to respond directly to it opens up the possibility of him gaining the advantage and forcing you to respond to his moves (forcing you onto the defense)
The endgame is putting the king on either side of the board in a position covered by 2 or 3 pawns that invites the opponent to seek a trap via a rook, queen or combination while you’re sending one or more pawns across to be converted to queens. Generally queening a pawn provides you with a powerful enough advantage to close.
Thanks for corrections; I am a novice and bad chess player and the description seems ill-written but I got the general drift.