a lot of people played the piano in the orchestra

None of Beethoven's symphonies has a piano part. He wrote five concertos for piano accompanied by orchestra, and a Fantasy for piano, chorus and orchestra.

vrienden, het leven is de moeite waard!

It's the violin, piano is rarely used in orchestra pieces.

No, a piano is an instrument. An orchestra is an ensemble of different kind of instruments. The piano does not have a place in the average orchestra. It may however play with an orchestra in a concerto. Pianists can also play arrangements of orchestral pieces.