Normally it means the master cylinder has failed and needs replacing. It can also be a leak in the system or the master cylinder is extremely low of brake fluid.
Hovering your foot over the brake without actually pressing on the brake
Take your toe and pick UP on the brake pedal. The brake pedal may not be returning as it should.
If you mean the switch that puts the brake lights on and off when you step on the brake pedal then it's located where the brake pedal is, can't miss it.
Generally it means you have your foot on the brake pedal.
depress the brake pedal and turn the engine switch to the start posiiton and start the engine,,, Does this mean to hold the brake down until you hear the engine start.
It sounds like you have a faulty micro switch on the brake pedal.
probably a vac. leak check your brake booster
If you mean (brake light) switch, the answer is yes. It is located at the top part of the brake pedal assembley.
A vibrating brake pedal is an indication of a warped rotor. Noise is common to disk brakes but depending on the noise it can mean that the brake pads are worn out and you are due for a brake job.
to not let go at the brake pedal once you press it.
your rotors are warped its gonna be a kinda pricey fix :-\
if you mean the brake light on the dash... fill your brake fluid as it's probably low If you mean the brake lights outside the car, your switch is shorted and needs replacement, or you need to lift your foot off the pedal