So EVs have something called regenerative braking, it's not braking in the sense it doesn't use the conventional, friction/hydraulic brakes, it engages the motors as generators, that creates resistance and slows the car - it also generates power back into the EV battery system.
Think of it in terms of how engine braking "feels", especially if you've driven a manual.
The Tesla, not only slows the car down, but can be set to bring it to a complete stop and hold. So you let off the accelerator, the car starts slowing, comes to a complete stop, foot totally off. Then you use the throttle again to get rolling - all with "one foot". You can also configure it to creep, more like a traditional car, so you have to hold it with the friction brakes.
You can still use the friction brakes to bring the car to stop quicker as desired, like on a road course 
