A Newtonian reflector uses a parabolic mirror to reflect the image back up the tube to an angled mirror near the front of a telescope. Mirror designs are more compact and often more affordable, but may require calibration or 'collimation'.
A Maksutov-Cassegrain reflector uses mirrors too, but the secondary mirror at the front bounces the image back down the tube and through a hole in the main mirror at the rear to an eyepiece or a camera adaptor at the back. These are like the 'mirror lenses' once popular (and still made) for cameras.