A Liquid Mirror Telescope is a Reflector Telescope whose Primary Mirror is formed of spinning liquid, such as mercury. Under Gravity, this creates a Parabola, useful for many types of reflecting telescope. However, the resulting mirror is in a fixed position, aimed straight up, though very slight aiming can be accomplished by moving the rest of the optics, at the expense of the quality of the image.
An example liquid mirror telescope is the Large Zenith Telescope (LZT).
Large Zenith Telescope (LZT)