The main scales we have in western classical music are the major, minor (harmonic and melodic), chromatic and whole tone scale.
To talk about scales more easily, it will help to discuss terminology a little. Lets start by having a look at the major scale (in the key of C major).
C major scale has no sharps or flats, which looking at a piano keyboard means that it is all the white notes from C to C.
It can help to think of each note as being a degree of a scale e.g. I - tonic, V - dominant etc. The tonic is the most important and stable degree of the scale.
An octave refers to the 8 (oct) step interval from one tonic to the next - C D E F G A B C. Scales on violin and viola will tend to span 1, 2 or 3 octaves, raising and falling back to the first tonic played.
In following posts, we will look more closely at the details of the different scales.