In American football an "interception" refers to when a player on defense catches a forward pass thrown by a member of the offense, thus "intercepting" a ball that was intended for a receiver on the offense. Upon catching the ball, the intercepting player may then attempt to return the ball as far as he can in the direction of his own end zone before he is tackled by a member of the offense. If he is tackled, his team takes possession of the ball on offense at the spot where he was tackled. If he makes it all the way to the end zone, he scores a touchdown, known in this instance as a "pick six."
As of this writing, the all-time record for interceptions in a single season in the NFL is 14 by Night Train Lane in 1952, and the all-time record for interceptions in a career is 81 by Paul Krause. On a more ignominious note, the all-time record for interceptions thrown in a single season is 42 by George Blanda in 1962, and the all-time record for interceptions thrown in a career is 336 by Brett Favre.