Source : Free On-Line Dictionary of Computing

field effect transistor
     
         (FET) A {transistor} with a region of {donor}
        material with two terminals called the "source" and the
        "drain", and an adjoining region of {acceptor} material
        between, called the "gate".  The voltage between the gate and
        the {substrate} controls the current flow between source and
        drain by depleting the donor region of its charge carriers to
        greater or lesser extent.
     
        There are two kinds of FET's, {Junction FETs} and {MOSFETs}.
     
        Because no current (except a minute leakage current) flows
        through the gate, FETs can be used to make circuits with very
        low power consumption.
     
        Contrast {bipolar transistor}.
     
        (1995-10-05)