Direct current (DC) is a unidirectional flow of current through a conductor or wire. Most DC power supplies offer a specific ratio of current to amperage. Because most DC connections are meant to match the volt and amp requirements of the device, this also prevents the wrong plug from going into the wrong device. The most common use of direct current is to power small electronics.
The most common type of DC power supply employs a "barrel connector" or some other cylindrical tip to connect an electronic device to a wall socket via a step-down transformer, which is often housed in the large plug of the power connector. The female-connecting cylinder on the DC power supply fits around a pin on the electronic device and the actual connection is made inside the cylinder so as to prevent electric shock to the user.
A common variety of DC power supply is one which uses a snap and lock connection. A series of pins on the DC connector are surrounded by a metallic shell. The metallic shell has a divot which snaps and locks into a mate shell on the electronic device.
A Tamiya connector is a DC connector commonly used with a variety of voltages and systems. These connector types consist of a plastic housing which snaps onto a female casing. Tamiya connectors are often found in battery packs, chargers, automobiles and other places where a secure direct current connection to the power supply is a requirement.