Need of a brake fluid - honda cars-?

What is the purpose of brake oil/fluid in disc and drum brakes
is brake fluid really need for disc brakes
or are they only for drum brakes.
how much quantity of brake fluid is usually need for a honda 4 door sedan cars

Brake fluid usually is labeled DOT 3 or DOT 4 for either disc/drum systems or all disc as special ingredients for ABS systems are part of the mixture. When you press on the brake pedal the fluid is sent to the brake assemblies at each wheel. In disc systems the fluid presses a piston in the caliper assembly to squeeze the brake pads into the rotor to stop the vehicle. Drum systems utilize brake shoes to press against the drum to help stop the vehicle as rear drums are part of the parking brake assembly totally separate from the service brakes.

The brake fluid (never use anything else, like oil) is what transfers the Force of pushing on the brake pedal to the actual brakes at the wheels. Otherwise we would an outdated and inferior system of levers and rods or cables to transfer our 'push at the pedal' to the wheels.

Yes, disc and drum brakes are hydraulically actuated, therefore need brake fluid.

System total, end to end, equipped with ABS and Traction Control would probably need less than a quart, didn't look it up.

Brake fluid is what provides the transfer of force from the pedal to the bake cylinders on drum brakes and the pistons on disc brakes. It is absolutely required for both.

A 32 oz bottle is about $7. That would more than refill the whole system I would think.