1) Catch between bases 2) Nail a napping baserunner 
In baseball, a pickoff is an act by a pitcher, throwing a live ball to a fielder so that the fielder can tag out a baserunner who is either leading off or about to begin stealing the next base. A pickoff attempt occurs when this throw is made in an attempt to make such an out or, more commonly, to `keep the runner close` by making it clear that .....
A move by the pitcher to attempt to throw one of the runners on base out instead of throwing the ball home. Once a player makes a move toward home, they have to throw the ball home. Not doing so is an illegal pitching motion and will result in a balk.
A fast throw from the pitcher to a fielder who is covering a base when the ball has not been strike into play.