Couple possible things.
I had a bad battery that wouldn't hold enough of a charge to run the engine when you stopped (because the engine wouldn't be running fast enough to charge it).
Or, idle air control valve.
the brakes or the emrgen see brakes
Check your fuel system.
Press the brakes or down shift
The system on a car used to slow it down
By puting your feet on the brakes
THey slow it down, if the rider so wishes.
Friction
The weight of the objects or due to the force
"Brakes" make the whole car slow down.
pump the brakes and downshift.
Bicycle brakes allow the rider to slow down in a controlled manner and with out undue wear on the tires.
Is your car equipped with an ABS system? That keeps the vehicle from locking the brakes to prevent skidding. The brakes automatically "GRAB" on and off to slow without skidding