Rushing Yards is a statistic in football that measures how many yards a player gained or lost when rushing with the ball, without receiving a pass. The "rushing yards" numbers can be counted for individual players, or for teams; in single plays, full games, or full seasons. Rushing is a very common play in football, and so rushing yards is a very used stat by coaches and television analysts.
The rushing yard counting is based off the ball carrier's movement. That is if a player advances five yards by his own movement, his rushing yards number increases by five. The same happens if a player goes back by his own motion, yards are taken off his rushing yards total. However, if a player is pushed 2 yards back by other players, his rushing yards total will not be reduced.
Running backs are usually the players who rush the most and thus have the most rushing yards, but other players such as quarterbacks and wide receivers also have significant rushing yards numbers. In the NFL a good rushing yards number per game can be considered anything above 100, with the best running backs recording around 1000-2000 rushing yards per season.