A timing pass in football is a pass based on the timing of a play rather than a receiver being open. The play is often described as the quarterback throwing the receiver open rather than the receiver getting open and the quarterback throwing the ball. For example, a quarterback throws the ball to a receiver two seconds after the snap instead of checking if they're open first.
A comeback pattern has the receiver run straight out and then turn around and take several steps back towards the line of scrimmage. A good timing pass has the ball released just as the receiver turns around.
The receiver heads out in a straight line and quickly cuts out towards the sideline. If the ball is delivered to the receiver just as they make their break then they can do more with the ball after the catch.
Fades are commonly thrown in the back of the endzone. It involves a forward running route but it is slightly drifting towards the back corner of the endzone. The ball should be thrown before the defensive back has a chance to turn their head around to look for it. A well timed fade allows only the wide receiver to catch the ball.
In order to throw a timing pass the quarterback and receiver have to be on the same page. The receiver needs to make their break in their route just as the quarterback is releasing the ball. The best way to improve a timing pass is repeated practice.
Quarterbacks and receivers try to develop chemistry by practicing over and over with one another. By doing so they can get their timing down and be more effective when executing plays in which timing is critical.
A good timing pass is unbeatable, there is nothing a defender can do if the ball is delivered at the exact perfect time. However, a mistimed timing pass is disastrous and can easily result in a turnover.