Why does brake force and braking torque change?

http://phet.colorado.edu/simulations/sims.php?sim=...

For the Torque simulation,

- Set force to 1N

- Click on GO!

-Wait about 2 seconds, then set Force of Brake to 3N

The question:

Eventually the disc stops and the net torque is zero. This is because the braking torque changed as you can see in the graph. Why did it change?

My answer:

The brake force is responsive, so even though it is -3N at first, only -1N is necessary to stop the motion of the applied force of 1N.

As soon as the motion is stopped, the brake force becomes -1N to keep the net torque at 0 (which means braking torque is equal but opposite to applied torque).

My question:

Does my answer make sense? I was thinking along the lines of: braking force is similar to frictional force in that it is responsive—it can be -3N, but only -1N is necessary, so it doesn't use its "max"

When I asked my teacher about it, he mentioned something about different types of frictions -- kinetic and static. However, I don't really understand what he is saying because I'm not sure if the disc is "sliding" when it is rotating, so I'm not sure if it's the difference between kinetic and static friction. For example, a wheel on a car travels by static friction between the road and the point of the wheel touching the road.

Please advise. Any relevant concepts are welcome.

Thanks in advance!