Awesome! Friction occurs whenever a body moves or tries to move on a surface. If an object is just sitting on a surface, there is no friction.

Once we exert a force to the right, the force tries to move the block to the right. But then the surface exerts a frictional force on the block in the opposite direction. Because the net force is \(0\), the block doesn't move.

As we increase the force, the frictional force increases accordingly. Once we exert a force beyond the maximum frictional force possible (\(30 \, \mathrm{N}\)), the block starts to move.