So, car relays can be seen as a collection of two parts: the control circuit for coil operation and the main circuit for contact operation. In the control circuit of a relay, there is only a small working current. This is because the contact capacity of the operating switch is small and cannot be used to directly control loads with high electricity consumption. It can only be controlled through the contacts of the relay to make and break.

In a relay, there can be multiple normally open contacts, normally closed contacts, and switching contacts. The normally open contact is in the disconnected position when not powered on, the normally closed contact is in the connected position when not powered on, and the switching contact can switch between the normally open and normally closed states.