From the Wikipedia:

In American football, a touchback is a ruling which is made and signaled by an official when the ball becomes dead behind or above a goal line (i.e., in an end zone) and the team who is attacking that goal line is responsible for the ball being there. Responsibility is determined by which team gave the ball the impetus to travel over or across the goal line. Such impetus may be imparted by a kick, pass, fumble, or in certain instances by batting the ball. A touchback is not a play, but a result of events that may occur during a play. A touchback is the opposite of a safety with regard to impetus since a safety is scored when the defending team is responsible for the ball becoming dead behind or above its own goal.

In standard outdoor American football, the team awarded the touchback receives possession of the ball at its own 20-yard line, except in college football, where the team awarded the touchback receives possession at its own 25-yard line on kickoffs and free kicks after a safety as of the 2012 season. In arena football, and other indoor football games, a touchback results in the team awarded the touchback receiving the football at its own five-yard line. This can result from any of the above events except for punting, which is not a part of arena football.

In Grid iron is the same as standard outdoor American football

Regulus wrote: thank you, I wondered that the touchback happened 5 times in this match of today.

Could be because his field goal setting is too short, he then punts instead.. If you add a match link it would be easier to determine