In the pro-formation, the two running backs line up behind the QB one to each side. The reason this is called a 28 sweep, is because the no. 2 RB runs to the 8 gap, hence the 28. Since he receives the ball as a pitch and they are running wide, it is a sweep play. So that how we get the name, Pro 28 Sweep.
The QB opens up to the no. 2 RB side and as he is swinging open, he pitches teh ball quickly to the 2 RB. As soon as the ball is snapped the two RBs start running the RB will most likely receive the ball when he is directly behind the QB or later. Everyone blocks downfield, especially the WRs.
Of course, the play can be run backwards. You can run it as a 47 Sweep. The no. 4 RB gets the ball and runs left to the 7 gap. The play can be reversed at the line of scrimmage or in teh huddle. The QB can check how the defense lines up and decide what to do. The QB can also decide if he wants to motion the TE or not.
In backyard football, the QB usually has the ball in his hands and can turn around and pitch it. This play works well if you have two very capable running backs and can run either way. The defense will always be confused. Another trick to use in backyard football is to always run the play to the weaker side. Not all players can tackle or are big, so you can just run it to the weaker side.
Very simple, very easy to use.