What exactly is the difference, larger in viola, different strings, treble clef or bass clef? Thanks.

vc

The viola is bigger than the violin. It sounds thicker.

Violin clef: treble.
Viola clef: alto (treble clef is used for very high notes).

Violin strings: 3G, 4D, 4A, 5E.
Viola strings: 3C, 3G, 4D, 4A.