5 terminals.


or almost any auto part store. Some have molded on mounting tab (easy to cut off)

Diagramatrically... is that a real word?

Anyway, here's what you get;

85 or 86 are the "trigger" terminals. One of them is hot (let's say 85), the other is grounded, machts nicht which one, power on/off operates a tiny magnet in the relay
30 is the power source you are directing
87 is powered until the current is removed from 85 (or interrupting the ground wire)
at which point the power is directed over to 87a.
One of the other is always "on". To kill both 87 and 87a you interrupt power to 30

The four terminal version operates exactly the same, except without 87a, it functions only as a simple on/off switch.

eidt -Bosch relay 61361391397 is described as a "diode starter relay".