Orchestra

Orchestra is a large group of musicians with strings, brass, woodwind sections and almost always a percussion section as well.

A small-sized orchestra of about fifty or fewer musicians is called a chamber orchestra.

A full sized orchestra of about 100 musicians is called a "symphony orchestra" or "philharmonic orchestra".

Classical Orchestra are composed of the following:

Woodwinds
2 Flutes
2 Oboes
2 Clarinets in B-flat, A
2 Bassoons

Brass
2 or 4 Horns (in any key)
2 Trumpets (in any key)

Percussion
Timpani

Strings
6 Violins I
6 Violins II
4 Violas
3 Violoncellos
2 Double basses