This should help. Let's look at the evolution of the pass rusher like we do the evolution of man:
Monkey - That's a defender that gets nullified at the line of scrimmage. He can still make a play of a fumble rolls to his feet or of a QB runs into him, but overall he's just taking up space.
Walking Monkey - He's able to evolve into moving forward and creating a
pressure. This typically helps the team more than just taking up space.
Walking Monkey + Stick = He's able to pressure the QB and actually make contact as he's letting go of the ball. Statistically this would be a
knockdown. This typically helps his team more than just getting a pressure.
Walking Monkey + Spear = This dude actually got to the QB while he still had the ball and it resulted in a
sack. This typically helps the team more than just getting the knockdown.
Walking Man = This fully evolved specimen not only gets to the QB before he releases the ball causes a fumble. This is called a
strip sack. Based on the number of defenders trying to get to the same area and that the OL is largely not looking in that direction it has a high chance of being recovered by the defense.
BTW, if your god won't let you use evolution as an example you should know he told me to post this as a test. If you go along with the example he'll totally let you into where ever he's currently keeping you out of.
And, if your god is a she that's probably just a cult and your cult chick told me sort of the same thing, but asked me to join in a creepy AMWAY way.