Finale divides percussion into two categories: pitched and non-pitched. Pitched percussion (xylophones, timpani, bells, etc.) behave like any other pitched instrument in terms of how they are notated. Non-pitched percussion, however, requires different treatment. A single percussion staff is often used to write for multiple instruments with each line or space representing a different instrument rather than a different pitch for the same instrument. Additionally, some percussion instruments may share a line or space with another instrument, each indicated with its own notehead symbol.
To keep all of this simple, Finale uses Percussion Layouts and maps to control notation and playback, which are most often handled for you automatically when you use the Setup Wizard. When you select a percussion staff, Finale selects the appropriate Percussion Input Map that will interpret information from your MIDI keyboard (if you’re using one) and convert it to a specific percussion instrument (called its Note Type), Percussion Layout to control the position of a Note Type on the staff, as well as the noteheads that it will use and a Percussion Output Map to translate Note Types entered on a staff into playback sounds.