What this part physically is
The G3R-202SLND-C24: That single voltage label is the headline control-side rating that decides coil compatibility when specifying into a 24 VDC control cabinet.
Where a G3R-series SSR sits in a panel
Solid state relays of this footprint replace electromechanical relays where the application needs silent switching, long mechanical life, and no contact bounce — typical loads are heaters, solenoids, and small motor starters driven from a 24 VDC PLC or controller output.