LogFAQs > #929612646

On a kickoff when the ball is kicked out of the end zone or the player catches it in the end zone and kneels down, play begins at the 25 yard line rather than if ran back, where the dude is tackled or steps out of bounds.

On a punt it is a little different. If the ball is kicked and touches the end zone it is a touchback(merely touching the end zone. Doesn't have to roll out.) It can roll into the end zone on a punt after falling in bounds. You wouldn't catch it and kneel down for a punt just let it roll out