That outlet is called a ground-fault circuit interrupter (GFCI). It’s there to protect people from electrical shock, so it is completely different from a fuse.
The question on appliance plugs talks about fuses. The idea behind a fuse is to protect a house from an electrical fire. If the hot wire were to accidentally touch the neutral wire for some reason (say, because a mouse chews through the insulation, or someone drives a nail through the wire while hanging a picture, or the vacuum cleaner sucks up an outlet cord and cuts it), an incredible amount of current will flow through the circuit and start heating it up like one of the coils in a toaster. The fuse heats up faster than the wire and burns out before the wire can start a fire.
Read the full article here:
http://home.howstuffworks.com/question117.htm
