The main components that stops the aircraft are the brakes and spoilers and secondary would be the reverse thrust and flaps.
When a airplane lands it still has some velocity and that velocity still creates lift.
When the spoiler goes up it stops the wing from create lift and sits the plane on the ground, so the brakes have more efficiency.
Some aircrafts would need twice or three times longer runways to stop with the spoiler inop.
As a secondary resource there are the reverse thrust and the flaps, witch when is full down creates more drag than lift and helps the aircraft to stop.