See also mains for specific countries and external links.
In the United Kingdom, Republic of Ireland and Singapore, which use 230 volts 50 Hz, large plugs with three rectangular pins are used. The two horizontal pins are live and neutral, while the larger, vertical third pin is the earth connection. Plugs contain interchangeable fuses connected to the live pin, and rated at 2, 3, 5, 10 or 13 amps depending on the amount of current drawn by the appliance.
Most European countries (230 volts, 50 Hz) use plugs with two round pins. Many plugs also have an earth socket which is penetrated by a pin on the outlet. A few households in Europe have 110 volt systems.
North America (115 volts, 60 Hz, 15 A) uses plugs with narrow, flat vertical pins. A third, round or sometimes horizontal, pin is used for earth on many appliances. Appliances requiring more than 1500 watts use different connectors, with standards existing through 480 volts 200 amps.
Australia (230 volts 50Hz, see mains) uses three-pin plugs with similar pins to the North American design, but set at an angle, plus a third longer pin for earth. Two-pin plugs without the earth pin also exist and can plug directly into a three-pin socket where earth is not required. All outlets except shaver sockets but including extension cords must by law have the earth connector. The standard outlet is 10 amps, a compatible 15 amp socket has a larger earth pin so that 10 amp plugs will fit 15 amp sockets but 15 amp plugs fit only 15 amp sockets.
It should be noted that some 60Hz appliances will work on 50Hz power but others will not and may even catch fire, as 60Hz allows use of smaller and lighter coils in motors, ballasts and transformers. See inductive reactance. While changing the voltage is relatively easy using a readily available transformer, frequency changers are rarer and more complicated.
Any additions/elaborations/corrections to this list are more than welcome.