Percussion includes all of the drums. This means snare drums, bass drums, toms, timpani, maracas, triangle, gongs, bongos, claves, castanets, cowbell, marimba, chimes, bells, vibraphones, etc. These instruments are usually hit with either drum sticks or appropriate mallets, and along with bass and piano, they belong to the rhythm section.
The percussion section serves as a means of keeping the ensemble as a whole on track. The can be found in practically all ensembles except for chamber orchestras and choirs. In jazz and pep bands, a drum set typically carries the band, but with larger bands and ensembles the different drums and auxiliary percussion are separated.