"Medium" is a channel, or a vehicle, or a conduit, or a material, that something
travels through in order to get from place to place.
A Medium of Instruction is the means or process by which learning travels
from the teacher to you.
Here are a few that I can think of right now. I'm sure you can come up with others:
-- lecture
-- printed text
-- Powerpoint presentations
-- recorded lessons with soft music in the background
-- colorful drawings
-- flashy billboards
-- famous singers reciting trig identities
-- numbered blocks
