An (electrical) adapter or adaptor is a device that converts attributes of one electrical device or system to those of an otherwise incompatible device or system. Some modify power or signal attributes, while others merely adapt the physical form of one electrical connector to another.
Countries with ties to Europe use 230 volt, 50 cycle power plugs and sockets. While many countries use the same 230 volt systems, there are a variety of different connectors used. Difficulty arises when moving an electrical device with a unique plug to another country with a different socket. An electric power adapter sometimes called a travel plug, may enable a plug from one region to use a foreign socket in another region. When traveling to and from continents that use 120 volt 60 cycle power, using a travel adapter is a safety hazard, check on the list of voltage by country.
An AC adapter, also called a "power cube" or "recharger", is a small power supply that changes household electric current from mains voltage ( either 120 or 230 volts AC) to low voltage suitable for consumer electronics.
For computers and related items, one kind of serial port adapter enables connections between 25-contact and nine-contact connectors, but does not affect electrical power- and signalling-related attributes.