Give something a push and it doesn't slide forever — it slows down and stops. The force that slows it is friction: a gripping, dragging force that appears wherever two surfaces rub together, always pointing against the way things are moving.

Rough surfaces (carpet, grass) grip hard — lots of friction, so things stop quickly. Smooth, slippery surfaces (ice, polished floor) grip barely at all — little friction, so things slide a long way.

Give the sled the same push on three different grounds. On ice it glides for ages; on carpet the big friction arrow stops it almost at once. Notice the friction arrow always points backwards — that's what makes it slow down.