Yes and NO!
They are each current carrying switches that cause an action. They both also have other functions. A fuel pump relay decides that a motor is off because the rpms are below 300; thus potentially saving lives in an accident. It also shuts down the fuel pump at a certain rpm to save the motor.
The OVP relay uses a zener diode to short circuit all power surges over some voltage. It clips all voltage spikes through the fuse. So no, it is not just a device that turns things on and off!
Bosch Master, ASE Master, L1
33 years MB technician