This is a small orange marker placed at each of the corners of the end-zone of a football field. These markers are usually made of a padded material. They are used as a visual aid to mark the inside corners of the end-zone. In the National Football League, if the ball is in a player's possession and the ball touches the pylon, it is considered a touchdown. If the ball crosses on top of the pylon without actually touching it, it is still considered a touchdown. If only the player's body touches or crosses the plain of the pylon, no touchdown is called.
The pylons are not permanent and they move easily when hit. This is for safety reasons, as a permanent structure would hurt players moving near the corner of the end-zone. The pylon is considered part of the field; it cannot interfere with a play. The pylons were introduced because game officials needed an easy way to see the edges of the end-zone from a distance.