
Courtney M. answered 09/05/20
Experienced Online Violin Teacher
In most pieces written for orchestra, whether a full orchestra or an all-string ensemble, there are two violin sections, one viola section, one bass section. There are pieces with three violin sections, and I have seen a few with a second viola or cello section as well. There is no rule that you can't divide the sections differently. But you should know that there's a very good reason there are so many violins on the stage in the first place: it's hard to hear them over other string instruments as well as wind and brass instruments. If you make your sections too small, the parts you have composed won't be heard in performance.
The musicians in each section play the same part, with the exception of solos. It's very unusual for a single violin to play more than one voice. And this is true of viola, cello, and bass as well. Typically, any chords and double stops written in the music are divided between stand partners. The general rule is that the person who sits on the outside takes the top and the person who sits on the inside takes the bottom.