A space vehicle which receives TV and radio signals and transmits them back to earth. It is located 22,300 miles above earth in a geosynchronous orbit so that it is stationary in relationship to a fixed position on earth.
http://www.nielsenmedia.com/glossary/terms/C/
A device sent up into space used to relay telecommunications signals between two or more points. The main advantage of satellites is the relatively low cost of the earth station equipment needed to link up with satellites compared to stringing wire or fibre optic cable over very long distances.
http://www.telecommons.com/uploaddocuments/TelecommunicationsGlossary5.doc
A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications. Modern communications satellites use geosynchronous orbits, Molniya orbits or low polar Earth orbits.
http://en.wikipedia.org/wiki/Communications satellite