The word of the day is “pocket”. In football terminology, a pocket is the area from tackle to tackle where the offensive line protects the quarterback giving him an area to throw the ball. In a perfect play, it forms an arc, or a cup that can look like a fat “U”.
To show this, there are two graphics. Graphic 1 shows the play diagram presnap:
Graphic 2 shows the players as the play has developed, you can see the U shape of the pocket as it has developed and the receivers where they are in their route progressions with their defenders in tow.
As you can see, the Guards and Centers have their work cut out for them with 3 guys blocking 4. Hopefully the QB hits the TE/X for a touchdown.
If a defender beats a lineman and gets inside the pocket it is called a busted and or broken pocket. If multiple defenders bust through it’s called a collapsed pocket which usually results in a sack.
If the QB has a superior level of pocket presence, he can feel and sense what is happening and can step up in the pocket to throw, or break the pocket and buy time to find an open receiver or run the ball himself.