To refresh is to renew or revive — to make someone feel newly clean or invigorated. After a long, hot run, a glass of lemonade might refresh you.
You might refresh yourself by taking a shower or a nap, and you can easily refresh your breath by brushing your teeth. When you refresh your memory, you stimulate it, or get it going: "I looked over my notes to refresh my memory before the quiz." On a computer, you can refresh a page by updating it. Refresh comes from the Old French refreschier, "refresh or renew."