In cricket, a yorker is a ball bowled which hits the cricket pitch around the batsman's feet. When a batsman assumes a normal stance, this generally means that the cricket ball bounces on the cricket pitch on or near the batsman's popping crease. A batsman who advances down the pitch to strike the ball may by so advancing cause the ball to pitch at or around his feet and may thus cause himself to be "yorked". Yorkers are considered to be one of the most difficult deliveries to bowl.
Chris Schofield being bowled by a yorker
Yorkers are very difficult to play. Here a batsman defends against one in the nets.
A delivery or ball in cricket is a single action of bowling a cricket ball toward the batter. Once the ball has been delivered, batters may attempt to score runs, with the bowler and other fielders attempting to stop this by getting the batters out. When the ball becomes dead, the next delivery can begin.
Spinner Muttiah Muralitharan bowling to the batter, Adam Gilchrist