Team X gives the ball to coach, who gives team O time to set up their press, gives the ball back to team X who inbounds and has to get the ball across halfcourt on the dribble then give it to team 3, team O can steal the ball, score and keep pressing.
With a 24-second shot clock, they want to take time off the clock. They're not necessarily trying to steal the ball but steal seconds off the shot clock.
O1 plays behind X1, allowing a catch in front, O3 face guards and denies X1.
O2 also plays behind X2, pushing him down to the baseline, allowing a catch in front, then shades sideline. You have kept the ball out of the point guard's hands (and O1 denies a pass from X2 to X1).
O1 tells O3 that the ball is in, O3 drops and plugs up the middle, then looks to double-team if X2 dribbles up the sideline.
They do not want to give up any long passes, keep everything in front.
See Defence - Fullcourt man-to-man basics