Once the ball has been hit, however, the attackers can run towards goal so many attackers will try to float a high ball over the defenders in the hopes of winning a footrace to goal. As a result, the players must balance the risk of holding the offside line against the risk of losing the footrace. The ability of the keeper to quickly come off of his line is a large factor in this decision. This leaves a nice buffer zone that allows the keeper to see the ball coming in, but leaves a fairly small amount of space behind the defenders for the attackers to collect and control the ball. For free kicks taken from the opposing half, the defenders usually will not wish to drop off any farther than the estimated distance that the kick will travel and, if their team has speedy defenders, they may wish to hold at the center line or at the 10-yard mark, whichever is farther.
Penalty kicks are simply direct free kicks that are taken from the penalty mark.
The only difference is that ALL players from both teams must be 10 yards or more away from the ball AND behind it. Once the ball is struck, all players can charge into the box and ANY player can play the ball except that the kicker cannot play it again until it has touched another player from either team. That means that the kicker cannot play a rebound directly from the post but CAN play a ball which is touched by the keeper. Defenders will want to mark up on attackers and run in with them to try to prevent another shot if the keeper managed to save the initial kick. The only object of the defenders at this point is to get the ball out and the safest thing to do is usually to kick it over the nearest end-line.