midi for newbs - device

Midi "devices" can...
send out midi when keys are hit and knobs are tweaked - a "midi controllers"
receive midi and generate a .WAV file or send sound out your speakers - a "sound module"
or both

A midi controller keyboard sends out note and control messages on a "channel". Every device has 16 channels max. Channel 10 is (usually) dedicated to drums. Most controllers send notes out on one channel. You can tweak most controllers to do a "split" by messing with the (usually terrible) menus on the instrument. This sends lower notes out one channel and higher notes out another. But, typically a keyboard sends notes out on one channel.

A midi sound module receives midi events and creates audio. Usually listening on all 16 available channels. Some lame older ones don't do all 16. Again, channel 10 is usually a drum channel. The other channels (1-9,11-16) are used for melodic sounds. All sound modules have a list of available sounds to pick from. Sometimes you can load in new sounds. Often not. But the majority let you change the sounds with "control change" messages.