This allows a stim to trigger any scripts the object has. A script message consisting of the stim name and the word Stimulus is sent to the object. For anything to happen, the object must have at least one script that is configured to respond to such a message. For example, torches have receptrons for WaterStim, FireStim and KOGas which all have the action Send to Scripts. The Extinguishable script responds to the messages WaterStimStimuls, FireStimStimulus and KOGasStimulus by either turning off the torch or relighting it.
This is how scripts from NVScript.osm can be configured to react to stimuli.