Also referred to as pitched and unpitched percussion, the difference between tuned (pitched) and untuned (unpitched) percussion is that pitched percussion instruments can play melodies and have its pitch adjusted while unpitched percussion instruments cannot. Unpitched percussion instruments, such as maracas or the snare drum, have no discernible pitch and are used solely for keeping rhythm during the piece or adding aural color with interesting sounds.
According to the music dictionary from Virginia Tech, both pitched and unpitched percussion instruments fall into three main categories: idiophones, mebranophones and auxiliary percussion. Idiophones, such as chimes, maracas, xylophones and bells, are instruments that make sound through vibrations that occur upon striking, plucking, shaking or scraping the instrument. Mebranophones also create sounds through vibrations, but they must have a stretched membrane that is the main conductor of the sound. All drums are a form of membranophones. The third category, auxiliary percussion, is a bit of a catch-all category where all the other miscellaneous percussion instruments go. It's the category where most of the special effects instruments reside, such as whistles, sirens, and wood blocks. Often used for comic relief or dramatic affect, auxiliary percussion instruments add a bit of pazzaz to a song or orchestral piece, such as the blast of actual cannons that Tchaikovsky used in his famous "1812" Overture in E Flat Major Op. 49 (1880).