Wiring for a 12V AC relay module?
Both AC and DC relays should have two terminals for the coil - apply the appropriate voltage between those terminals to operate the relay.  For the relay you linked to, you would apply 12 Volts AC to those terminals.

Any relay will have two or more contacts for the contacts (the switch part of the relay)  Although the Amazon listing doesn't say, with 8 terminals that relay must be a DPDT (Double pole, double throw) type.

A schematic symbol for that relay would be:







simulate this circuit &ndash; Schematic created using CircuitLab

Circuitlab won't let me place the labels where I want - hope you'll understand things.

To operate the realy, you apply 12 volts between terminals "Coil 1" and "Coil 2".

The contacts for one pole of the relay are "COM1" - the moving contact, "NC1" Normally closed contact - connected to "COM1" when the relay is not operated, and "NO1" - Normally open - connected to "COM1" when you apply power to the coil (similar for COM2, NC2, and NO2).

You don't have to use both sets of contacts - only connect the terminals that you need for your application.

I don't understand what you mean by "This is because, unlike DC relays, I expect that AC relays only take 2 inputs (compared to 3); i.e. the relay gets triggered when electricity flows into the module. Is this correct?", but I hope I've explained that relay's operation sufficiently.