This is apparently a French usage. T1, T2, T3 ... T# corresponds an apartment with the indicated number (#) of main rooms (living room, dining room and bedrooms). The kitchen and the bathrooms are not included. Thus, an apartment with a living room and two bedrooms is a T3. Example: T2 = apartment with 1 bedroom + 1 living room. Example: T3 = apartment with 2 bedroom + 1 living room. See See: http://paris.angloinfo.com/countries/france/propjargon.asp and http://forum.wordreference.com/showthread.php?t=359359

[ Not enough information ] It could mean Terrace 1, Terrace 2, Terrace 3.