All forces are either pushes or pulls acting on a body. If you are driving a car and it becomes stuck, you may have to get out and push it forward to get it unstuck. That would be an example of a parallel force. All parallel forces act along the same line as the direction the object is moving. Parallel forces can act to move an object forward faster, or against an object to slow it down.
For example, you tie a rope around your waist and start running forward. If someone is holding on to the rope behind you and pulling backwards you could not run as fast as normal. On the other hand, if the person holding the rope was in front of you on a bike pulling you forward, you could run faster than normal. Both forces are parallel forces.
A perpendicular force is one that acts on an object at right angles to the direction of motion.
Suppose you are driving in a car and go through an intersection. As you enter the intersection, another car runs a red light and hits you in the side. The force of the car hitting you is a perpendicular force.