"An Enrolled Agent (EA) is a federally-authorized tax practitioner who has technical expertise in the field of taxation and who is empowered by the U.S. Department of the Treasury to represent taxpayers before all administrative levels of the Internal Revenue Service for audits, collections, and appeals."
Please go to the following page for more details:
http://www.naea.org/memberportal/Resources/ForTaxpayers/whatis_EA.htm