Traction
Traction is the grip between a tire and the road that keeps a vehicle from sliding.
Think of it this way
A damp sponge grips a smooth countertop better than a dry plastic bag does. The sponge has a rough, textured surface that presses into tiny bumps on the counter. That contact creates friction — the force that resists sliding. More surface contact means more grip, just like a tire with deep treads holds the road better than a bald one.
Explaining traction by grade level
Think about a go-kart racing on a track. Soft tires grab the road like sticky hands. Hard tires slip more, like shoes on ice. The grip between the tire and the road is what helps the go-kart turn and stop safely.