Even better explaination:
College football rules allow either team to score a one-point safety after a touchdown. Say that Team B blocks Team A's extra-point attempt, and a player on Team B picks up the ball on the 1-yard line. Looking for an opening, the player with the ball runs backwards voluntarily into his end zone, where he is tackled. Team A receives one point for the conversion safety, and the score is now 7–0. Team A then kicks off from its own 30-yard line, as after any touchdown. A conversion safety has occurred at least once in the NCAA, in a game between Texas and Texas A&M in 2004. Following the Longhorns TD from a blocked punt, the ensuing PAT was blocked and recovered by a Texas A&M player on the one yard line. The player tried to make a return, but was tackled in his own endzone for a one point safety.
Although exceedingly unlikely, college football's rules also allow the defensive team to score a one-point conversion safety on a PAT or conversion try. One possible scenario: Team B blocks Team A's extra-point attempt, and a player on Team B picks up the loose ball and runs towards the opposite end zone. Before reaching the goal line, he fumbles the ball and it is recovered by a player from Team A, who then voluntarily runs into his own (Team A's) end zone and is tackled. Team B would score one point for the conversion safety and the score would then be 6–1.