opengl is a graphics library while glut is not.
You use glut with opengl to handle graphics. glut handles with mostly
the input. It could create the graphics window, handle key input and some other fancy stuff. You use opengl to draw primitives onto the window
that glut creates.
but I have looked at this tutorial and it uses glut to make the window and print to it, how come?
Well it can do some printing stuff too, but its primary task is to create
the window and get inputs. You should use opengl to draw stuff. Of
course there are some draw stuff that makes your life easier, which
glut has, like drawing text or a sphere, among other things.