A plug adapter is a small device that allows you to plug your device into a wall in a country that has different electric plugs.  For example, the two flat prongs on a US plug won’t fit into the electrical sockets in Italy.  So, you need a plug adapter – insert your US plug into one end and plug the adapter into the Italian socket.  A power adapter is a power supply for your electronic devices.  It also goes by ‘charger’ or ‘AC adapter.’