In football, the offense can choose to either pass or run the ball to try and gain yards. The defense will try to predict what type of play the offense will run based on the formation, game scenario, and personnel of the offense. This way, the defense will have a greater chance of stopping the play.
In its simplest form, a draw is a run play that looked like it was going to be a pass play. Draw plays are often run out of a shotgun formation, which is usually used for passing plays. The quarterback will take the snap and drop back as if he is about to throw before handing it off to the running back on an inside run.
The offensive line plays an immense role in the success of a draw play. They have to use pass protection blocking before springing into run blocking techniques in order to fool the defensive front. This means one O-lineman will likely drop back a couple steps before sprinting forward to block a linebacker at the second level of the defense.
There is also a quarterback draw, in which the quarterback will tuck the ball and run with it himself. This is definitely less common than a traditional draw play, but it has the potential to be just as effective.
The blocking schemes of the offensive line often make or break a draw play. If a defense overloads the middle of the formation on a blitz, it is unlikely that a pass-blocking scheme will be able to create enough space for the running back.
Another possible drawback of a draw play is the time it takes to develop. Compared to other run plays, a draw takes a while to get going. This will work in the defense's favor if a linebacker or defensive lineman can read the play.