Can someone please tell me what the difference between indeed, obviously, and of course is?
They are used for emphasis. Let's say you and I are in a room that is blue and I say "the room is blue." Your response would be:
"Obviously, the room is blue." - I stated something we both could see and you are annoyed by that.
"Indeed, the room is blue." - You agree with me on the room's color or you are surprised by the intensity of the color.
"Of course, the room is blue." - You know the reason why the room is blue or you don't want to be sarcastic and / or make fun of me for stating the obvious.