According to Osho, reaction comes from the past—conditioned, mechanical, projected habits that make you a robot; response arises from the present—fresh, aware, and attuned to the real situation. Reaction repeats memory; response sees what is, creates space and understanding. Buddha exemplified response: he met an insult with presence, revealing freedom between stimulus and action.
A reaction is your old autopilot pressing buttons; a response is you pausing, seeing what’s really happening now, and then choosing.