Anaesthesia causes temporary loss of sensation or awareness through analgesia, muscle relaxation, amnesia, or unconsciousness. It enables painless medical procedures. There are two main types: general anesthesia causes unconsciousness and lack of sensation through suppression of the central nervous system, while local anesthesia numbs a specific body part by blocking nerve impulses between that area and the central nervous system. Local anesthetics block sodium channels in nerves to prevent action potential generation and conduction.