well... i think this must be in chorus, maybe... if so, then they would be an octave apart. I did band, so I know bass clef and treble clef.

The G cleff/alto cleff is the "traditional" musical symbol. It indicates the G line in the staff. The B cleff/viola cleff indicates the B line on the staff. I suspect this is what you mean by Tenor cleff. There is also the F cleff/Bass cleff. The differences are to make musical notation easier and reduces the number of notes above and below the staff. The G cleff looks like the letter G, the B cleff looks like the letter B and the F cleff looks like the letter F.

When the C-clef is placed on the third line of the staff, it is called the alto clef. When the C-clef is placed on the fourth line of the staff, it is called the tenor clef. "The alto clef: When the C-clef is placed on the third line of the staff, it is called the alto clef. As with all C-clefs, this line indicates the position of middle C. This clef (sometimes called the viola clef) is currently used for the viola, the viola da gamba, and the alto trombone. Formerly, it was used for the alto voice and by instruments playing a middle part (oboes, recorders, etc.) It occasionally turns up in keyboard music to the present day (Brahms' Organ chorales, John Cage's Dream for piano). The notes from the bottom line to the top line are: F3, G3, A3, B3, C4, D4, E4, F4, G4 - The tenor clef: When the C-clef is placed on the fourth line of the staff, it is called the tenor clef. This clef is used for the upper ranges of the bassoon, violoncello, euphonium, double bass, and trombone (which all use the bass clef in their lower and middle ranges, and in their extreme high ranges, the treble clef as well). Formerly, it was used by the tenor part in vocal music but its use has been largely supplanted either with an octave version of the treble clef when written alone or the bass clef when combined on one staff with the bass part." Source and further information: http://en.wikipedia.org/wiki/Clef#The_alto_clef