Question: What does a telescope mount do?
About the article "Telescope", section "Types of mount".

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This telescope, used exclusively for visual tourist operations is a 0.4m Meade LX200 telescope. 
The main instrument at Sherwood Observatory is a Newtonian telescope on an equatorial fork mount.
The telescope was initially constructed as a Nasmyth reflector but due to collimation problems it was converted in the 1990s to the simpler Newtonian configuration.
The telescope has stepper motor drive control with an electrical focusser.
The dome is electrically driven and will move automatically as the telescope tracks across the sky.
Various cameras can be attached to the telescope to record images and video and display what the telescope sees on a 2 metre wide projector screen in the lecture theatre from where the telescope can be controlled. 
 Hale telescope, telescope at Palomar Observatory in California 60-inch Hale, a telescope at Mount Wilson Observatory in California Hale (lunar crater) Hale (Martian crater)  
The Dobsonian design has the following characteristics: Altazimuth mount: An equatorial telescope mount with clock drive was left out of the design.
Equatorial mounts tend to be massive (less portable), expensive, complicated, and have the characteristics of putting the eyepiece of Newtonian telescopes in very hard to access positions.
Altazimuth mounts cut the size, weight and cost of the total telescope and keep the eyepiece in a relatively easy to access position on the side of the telescope.
The altazimuth mount design used in Dobsonian designs also add to simplicity and portability; there is no added mass or need to transport counter weights, drive components, or tripods/pedestals.
Setting up for hard tube dobs simply involves placing the mount on the ground, and setting the tube on top of it.
The weight of the Dobsonian style altazimuth mount is distributed over large simple bearing surfaces so the telescope can move smoothly under finger pressure with minimal backlash.
The altazimuth mount does have its own limitations.
Un-driven altazimuth mounted telescopes need to be "nudged" every few minutes along both axes to compensate for the rotation of the Earth to keep an object in view (as opposed to one axis for un-driven equatorial mounts), an exercise that becomes more difficult with higher magnifications.
The altazimuth mount does not allow for the use of conventional setting circles to help in aiming the telescope at the coordinates of known objects.
They are known for being difficult to point at objects near the zenith, mainly because a large movement of the azimuth axis is needed to move the telescope pointing by even a small amount.
Altazimuth mounts are also not well suited for astrophotography.
Large objective diameter compared to mass/cost *Low mass to objective size ratio: The Dobsonian design's structure as measured in volume and weight is relatively minimal for any given objective diameter when compared to other designs.
*Low cost to objective size ratio: From a cost perspective, a user typically gets more objective diameter per unit of cost with the Dobsonian design.
Good "Deep Sky" telescope: The Dobsonian design of maximized objective diameter combined with portability makes the design ideal for observing dim star clusters, nebula and galaxies (deep sky objects), an activity that requires large objectives and travel to dark sky locations.
Since these objects are relatively large they are observed at low magnifications that do not require a clock-driven mount.
Balance Issues: Designs that have the telescope tube fixed in relationship to its altitude bearings can be put out of balance by the addition or subtraction of equipment such as cameras, finderscopes or even unusually heavy eyepieces.
Most Dobsonian telescopes have enough friction in the bearings to resist a moderate amount of imbalance; however, this friction can also make it difficult to position the telescope accurately.  
A telescope mount is a mechanical structure which supports a telescope.
Telescope mounts are designed to support the mass of the telescope and allow for accurate pointing of the instrument.
Many sorts of mounts have been developed over the years, with the majority of effort being put into systems that can track the motion of the stars as the Earth rotates.
The two main types of tracking mount are:
 Altazimuth mount
 Equatorial mount