I can answer it at least for my car. You "depress" (meaning to press down) the pedal to the floor and it disengages, allowing the pedal to rise to the normal position (such as when the vehicle is in motion).

On some cars there is a handle, similar in size and placement to the hood release lever, so there can be some confusion if one is borrowing another's car. This handle is pulled to release the parking brake if the design of the pedal doesn't allow the operation described above. Usually the brake lever is labeled as such "PARKING BRAKE" or "EMERGENCY" and the universal (I guess it is anyway) symbol showing the opened hood is silk-screened onto the hood release.