General anesthesia means the entire body is "asleep" for surgery. This usually occurs in two stages. First, you are given a short-acting intravenous drug that will make you drift pleasantly off to sleep and lose awareness of what is going on around you. The second stage of general anesthesia keeps you asleep through your surgery.
Regional anesthesia numbs certain areas of the body so you do not feel pain. Common types of regional anesthesia are epidural, and spinal as well as peripheral nerve blocks such as a shoulder block. With regional anesthesia, you may be awake and aware, OR you may receive medication that will make you drowsy or keep you in a light sleep.
Monitored Anesthesia Care (MAC) is the "twilight sleep". During MAC anesthesia you get medicine through your IV that keeps you asleep. This type of anesthesia is commonly used for colonoscopy and cataract surgery.