How can I relay 120VAC with a raspberry pi?
To pick a relay, check:


Relay operation modes: (monostable, bistable, normally open/closed...)
Relay type (solid state, mechanical)
Output capacity: voltage and current. Make sure your load doesn't exceed these. Keep transients in mind: I recently had a mechanical relay fail because of the instantaneous current draw when charging a big filtering capacitor down the line.
Input requirement: voltage and current. Make sure whatever is controlling the relay can comfortably provide the required power to activate the relay.


Sounds like you've checked #1-3. The ebay page says that the relays will activate in response to an input above 2.5V (OK for a PI's 3.3V GPIO), but not how much current they will draw. So check the relay input current draw, and the maximum current the PI can source on GPIO to see if this relay board will work with a PI.