Suspension
Suspension is a system of springs and shock absorbers that connects a vehicle to its wheels.
Think of it this way
Set a box on four soft sponges. Push the box down hard. The sponges squish and then spring back up. The box bumps less than if it sat on a hard shelf.
Explaining suspension by grade level
A car has springs near each wheel. The springs soak up bumps in the road. They keep the car steady so the tires stay flat on the ground. Stiff springs help a car turn corners fast.