Welcome to musical instruments facts. A classical orchestra is composed of many instruments played by many musicians to make the wonderful sound orchestral instruments make.
The orchestra is broken into four families of instruments;
The Brass Instruments
The Percussion Instruments
The String Instruments have their name because they made with strings that are either bowed or are plucked. In the string section of the orchestra the principal violinist is called the concertmaster. He is the violinist who sits closest the the conductor and the audience.
In an orchestra there are about 10 first violinists, 10 second violinists, 8 violists, 10 cellists and 6-9 double bassists. The number changes depending on the orchestra, some have more than others.
The Woodwind Instruments have their name because they are musical instruments made out of wood and are played by wind. Before a concert you will hear the orchestra tuning. They tune to the "A" that the oboe plays because of the clear sound it can produce enabling the musicians to be able to hear a clear "A".
In an orchestra there are generally 2-4 flautists with one doubling as a piccolist, 2-4 oboists with one doubling as an english hornist. Also 2-4 clarinetists and 2-4 bassonists and one contrabassoonist.
The Brass Instuments have their name because they are made out of brass! The modern brass section has two families, the valved and the slide brass instruments. The valved brass instruments include all of the brass instruments except the trombone which is a slide instrument.
In a Classical orchestra there are 2-5 trumpets, 2-8 french horns, 2 tenor trombones, one bass trombone and one tuba.
Percussion came from a latin word which translates "to beat, strike". In the percussion family some instruments have definite pitch and the rest have an indefinite pitch. That means that the instruments with definite pitch can be tuned just like a violin or other instrument is tuned to play a specific pitch. The Piano, some triangles, the marimba, the glockenspiel, the xylophone and the timpani are all percussion instruments with definite pitch.
Did you know that there are some really great sites on the internet now that teach you everything that you need to know about playing music? A really great one for piano is Play-the-Piano.org. This site has some of the best explanations of Music Theory I've ever seen, with great diagrams that help you visualize the concept! I've used it myself :)