This article does not have any sources. (December 2011)
Administrators are people who organize things like businesses. All businesses have administrators. They make decisions, organize the people who work there and make sure that things are working alright and there are no problems. Their work is called "administration". The administrators are part of the "management".
Administrator is also the person in charge of some of the small territories of the United Kingdom, for example Ascension Island and the British Antarctic Territory which are too small to run their own government.