What is the function of the device in the picture. Unfortunately, I did not make a full diagram of how it was wired, but the hot and the corresponding neutral were connected by crimp-on leads on the right side. The hot was downstream from a lutron dimmer and there were three other 14/2 wires in the box which I'm not sure where they led to.
That is a contactor. With the proper electrical signal to a coil underneath it magnetically draws the switching plate across the contact points and closed the circuit. This type of unit is typically rated for 15 to 40-Amps. It is an electrically operated switch for heavier loads.