What is ReAct compared to Plan-and-Execute agents?

ReAct interleaves thinking and acting, deciding the next action based on the previous observation. Plan-and-Execute first generates a complete multi-step plan, then executes the steps in order. ReAct adapts better to surprises mid-task, while Plan-and-Execute is more efficient when the path is predictable. Many production systems combine both, planning at the high level and reacting within steps.