A "preset" is the sound that you play or perform with in the Proteus 2000, sometimes called "programs" by other people. A preset consists of between one to four "layers" where each layer can have its own unique INSTRUMENT. An instrument is simply a grouping of digital audio samples stretched across a range of keys. To make the chosen instrument sound more realistic, the preset is programmed so as to manipulate the sound using patch cords, real time controllers, effects, filters, etc. There are 1536 presets in the Proteus 2000. All are programmable and can be saved in one of the 512 user preset locations. The user presets are "copies" of the ROM presets, so don't worry about losing presets by saving your edits. The 32MB standard ROM that comes in the Proteus 2000 has 1173 instruments which can be used to create presets. AS you add more sound ROMs to your Proteus 2000, they will have their own presets that come with them that increase the total number of presets available in the unit.