So here's your situation. It's 2nd and 10 after a broken up running play. The offense sends out the Tight End (the receiver/blocker who normally lines up at the end of either side of the offensive line) in favor of a 3rd wide receiver. The offense now has 2 receivers to the right, one to the left, those 5 blue dots in the middle represent the O line, the guy right behind the center is the QB, and the two dots at a 45 degree angle on either side are the Halfback on the left, and the Fullback on the right. The defense (brown dots) responds by subbing out for the Nickle, a formation with four defensive linemen (brown dots directly opposite the offensive line), two linebackers (directly behind the defensive line), and five defensive backs (everyone else). From the left to the right you have a corner back, the free safety, strong safety, and two more corner backs. The offense here is going to try and gain 5-10 yards safely UNLESS the defense breaks down (generally meaning someone in pass defense fucks up). It really all depends on how the defense reacts as to what the QB will do Now no two coaches call the same play the same thing. In fact allot of times they use code words so that if the defense overhears the play they won't know what's going on. That would make teaching you waaaaay to hard so we'll just give this play a basic name. Post slot slant HB flat, meaning that the wide outs (wide receivers on the far sides) run straight ahead, the slot receiver (3rd receiver on the inside) runs a slant (straight ahead for 7ish yards then 45degrees to the opposite end of the field), The halfback will kind of run a relaxed curvy rout to the flat (where the sideline meets the line of scrimmage), and the beefier fullback will stay in the pocket when the QB drops back as an extra blocker in case the defense wants to rush all six men in the "box" (the defensive line+ line backers). Now the defense will run "Cover 2 Man", That means that the Free Safety and the Strong Safety will drop back into their area of responsibility (indicated by the blue circles), the defensive line will rush the QB, and the line backers and corner backs will be assigned to receivers and backs as indicated. The wide receivers will be guarded much like you guard someone in basket ball, while the linebackers will take a more "wait and see approach" trying to ensure that the HB and the FB stay underneath them while accounting for the 3rd back, the Quarterback. note to football fans: yes I know this is way over simplified at an NFL level, I'm just trying to show the concepts Here's the play in motion. The wide receivers on the far sides trying to do two things, get behind the safeties and the corner backs. This would allow the quarterback to put the ball "over the top" of the defense for a big play. The slot receiver here is already in trouble because his defensive back has already gotten between the him and the QB. To make matters worse he's running straight for that blue circle which is the responsibility of the Free safety. This shows you the deference between "Zone Coverage" (blue circle) and "Man coverage" (red line). Once he's in that circle he will be "Bracketed" (surrounded on more then one side by a defender) and discounted by the QB. Likewise the QB should notice that the Wide receiver on the far right is well guarded and even if he gets behind the Corner Back he'll still have the Strong Safety to contend with. 3 seconds into the play and the QB has already lost two options. At this point the QB can do one of two things, hope the slot receiver will draw the Free safety down and allow his wide receiver on the far left to get behind his corner back, or force the issue developing in the left flat. LOLB (left outside linebacker) who's guarding the halfback is in a world of trouble. He still has time to get on the HB before the ball is thrown but in doing so opens the left flank up for a QB scramble (run). Now he has a decision to make. For the time being he'll play the HB "soft" (meaning he'll give him a touch of space but guard him), the space will be used to keep an eye on our QB, who's yet to make his decision. The problem is, the QB has already won. As you can see the Slot receiver is indeed bracketed now, and the receiver on the right side is in no better shape. The QB can make the long throw to the Left wide out but it's risky, his defensive back is still pretty tight on him so you can't rule out an interception or a broken up play which would make it 3rd and long. He'll save that option for a rainy day. The Halfback has reached the flat, drawing out the LOLB with him. The Quarterback takes this opportunity to role out of the pocket to his left and make a scramble. The LOLB sees this and must now commit to stopping the run, he's ran out of choices and leaves the HB to take down the ball carrier. but this isn't a running play. The quarter back who's still behind the line of scrimmage throws the ball to the HB who's now open. The secondary (all the people guarding those receivers) are way to deep to make a play on the ball. The HB catches it and runs probably for 15 yards or so. This worked because the QB ran out of the pocket, had he stayed home the only open receiver would have been that risky throw to the far left side, which could have caused 3rd and 10 and the eventual punt. This time the QB played the LOLB well, developed a passing lane to an open player. recognized the secondary was too deep to back up the LOLB, and made the play. Trust me it gets WAY more complicated when you start zone blitzing on defense, but hopefully you can appreciate the mental aspect of the game a bit more now.