Hi,

Am I right that (at least in the HVAC context), a relay switch is a
switch that turned on by a passing current.

For example, in the compressor, there is a line voltage cable that's
always on, but the unit does not turn on until the thermostat completes
a circuit thereby flipping the relay switch on.

Is that correct?

Also, if a contact in the thermostat is labeled "Fan Relay", does the
word "Relay" refer to the relay switch in the fan? (In that case, why
not just say "Fan"?)

Thanks in advance,

Sam