Understanding of "Actus Reus" in Criminal Law: A Real-World Example Needed

I'm struggling to grasp the concept of "Actus Reus" in textbooks. They explain it as a voluntary act, but I need something concrete to relate it to. A case or scenario would be super helpful, but an example from daily life would suffice. For instance, if a person accidentally knocks down a vendor's stall while in a hurry, is that an Actus Reus? Or does it become one only if he tries to flee the scene? Can anyone shed some light on this?