Some teams like to run the ball more than pass. Some teams prefer to pass. This all depends on the type of players a team has and the style of play the coach like to use. The defense uses ends , tackles and nose guards to stop the run. Linebackers help in runs and passes.
Cornerbacks try to stop passes.
The strong safety helps against passes and runs. The safety prevents long plays. The defensive formation usually matches up with the offense. But the defense can try to do different strategies to stop the offense. The defense can move players around to cause the offense problems.