MIDI (Musical Instrument Digital Interface) is a protocol developed in the 1980's which allows
electronic instruments and other digital musical tools to communicate with each other. 
MIDI itself does not make sound, it is just a series of messages like "note on," "note off,"
"note/pitch," "pitchbend," and many more.  These messages are interpreted by a MIDI instrument 
to produce sound.  A MIDI instrument can be a piece of hardware (electronic keyboard, synthesizer) 
or part of a software environment (ableton, garageband, digital performer, logic...).

General MIDI Percussion Map

GM always uses MIDI Channel 10 for drums.

MIDI NoteInstrument
35Acoustic Bass Drum
36 (C2)Bass Drum 1
37Side Stick
38Acoustic Snare
39Hand Clap
40Electric Snare
41Low Floor Tom
42Closed Hi-Hat
43High Floor Tom
44Pedal Hi-Hat
45Low Tom
46Open Hi-Hat
47Low-Mid Tom
48 (C3)Hi Mid Tom
49Crash Cymbal 1
50High Tom
51Ride Cymbal 1
52Chinese Cymbal
53Ride Bell
55Splash Cymbal
57Crash Cymbal 2
59Ride Cymbal 2
60 (C4)High Bongo
61Low Bongo
62Mute High Conga
63Open High Conga
64Low Conga
65High Timbale
66Low Timbale
67High Agogo
68Low Agogo
71Short Whistle
72 (C5)Long Whistle
73Short Guiro
74Long Guiro
76High Wood Block
77Low Wood Block
78Mute Cuica
79Open Cuica
80Mute Triangle
81Open Triangle