Let me suggest a couple of refinements to Roy's basically correct
answer:

Track is the motion you are making over the ground. It is what a GPS shows.

Might be clearer to the questioner if we say that track is the way you
actually went, regardless of what you intended. Exactly as an animal
leaves tracks.

Bearing is the direction from you to someplace else. It can be absolute
(bearing 270 degrees) or relative (9 O'Clock).

I would say that Course and Track mean the same thing. They both refer to
your motion over the ground.

Course is what you intend to fly. It is the line you drew on the
chart before going to the airport. If everything works out perfectly,
your track will be the same, but if the winds are not as forecast, or
you aren't paying enough attention to the compass, the two will
differ.

Heading is what direction the nose of the plane is pointing. It's what you
read off your compass or DG.

That's your "compass heading." Magnetic heading is the compass
heading corrected for deviation (instrument error). True heading is
magnetic heading corrected for variation-- caused by the fact that the
magnetic pole is not at the North pole.

Might add the word "drift"--which is the difference between heading
and track, caused by wind.