Ordinary switch basically operates as a make or break switch. When it is turned on, the circuit is connected and when it is turned off, the circuit will be disconnected. So, it is a type of one-way switch.
Bell switch remains active only when an external pressure is acting on it, and becomes inactive once the pressure is removed. So, it is a momentary type of switch.
Two-way switch allows the control of a single device from two different locations in the room thereby making the control/operation of the device very flexible and easy.