Tau Ceti III was the inhabited third planet of the Tau Ceti system. This planet was located proximately eight light years from Earth. (TNG: "The Naked Now", production art)
Prior to stardate 41775, Jean-Luc Picard first met Walker Keel at "quite an exotic" bar on Tau Ceti III. (TNG: "Conspiracy")
"tow (rhymes with cow)- set-ee 3" was the pronunciation for this planet's name from the script pronunciation guide.