Swerve is pretty much the opposite of cue ball deflection. When you hit the cue ball on the right it is initially forced or squirted over to the left but what happens next is swerve. The cue ball starts to come back in the direction of the side spin applied; in this case it would start to come back to the right.
Picture a big curving masse shot and you have a great example of cue ball deflection and cue ball swerve. First the ball is struck firmly on one side forcing it outwards and then the cue ball spins back in the direction of the applied spin.
Both deflection and swerve occur on just about every shot struck with sidespin. The problem is they’re both practically invisible to the untrained eye. Even the trained eye doesn’t actually see the deflection but knows it is going to happen or has happened.