Recovery time is a kind of “stun” – it is the timeframe after a move has been active. During this time, you are “recovering” from performing the move and will be generally unable to do anything even if you see it coming. This is the latter of the parts of a move’s execution where you are left open, consequently.
If this opening after a move is long, it will be easier for the other person to score a counterattack, so when your combo attempts are blocked, it follows that you should do your best to stop it on a move that doesn’t have as much recovery; this minimizes frame disadvantage.