Have you ever gone into a dark room and heard something scurrying across the floor and felt your pulse quicken and your heart race? You were scared — afraid.
When you are scared, you are frightened or alarmed. It can be a momentary thing: hearing a car screech outside your house and worrying that your dog just got hit. It can be longer: you might be scared for weeks or months after a medical diagnosis. While the verb is usually associated with a single person or small group, you might also apply it more generally: a fast-moving tornado could have scared a whole town.