Could somebody explain the difference between OpenGL and OpenGLES please?
The latter is a subset of the former, suitable for Embedded Systems (hence the ES suffix)
And where does GLUT fit into the picture?
GLUT is like LCL, it abstracts windowing, event and input management of underlying platform, albeit in a much simpler way. It doesn't exist for OpenGL ES (along with GLU) although porting is probably possible. The design is old and I don't recommend using it for new projects, GLFW (and GLFM for mobile, largely inspired but is a different project and API) is better suited.