A mount can make or break your telescopic experience. You can have
the best optics, but a poor mount can render your experience into
a frustrating one. Because a telescope magnifies everything the
effects of vibration and the drift produced by the rotation of the
earth is also magnified.
Alt-Azimuth Mounts
The simplest kind of mount is the Alt-Azimuth. Alt-Azimuth mounts
move in the horizontal (azimuth) and the vertical (altitude) directions.
This kind of mount is great for terrestrial viewing as the motion
is defined by the orientation of the tripod to the ground (i.e.
up/down - left/right).
Examples would be a primitive Dobsonian mount, sort of a "Rocker-box-on-a-Lazy-Susan",
generally used for large homemade Newtonian type telescopes, or
most computerized telescope mounts which handle tracking celestial
objects in two axes using a computer.
Equatorial Mounts 
Because the earth rotates 15 degrees an hour, the sky appears to
revolve around the North Star (Polaris). To simplify the movement
of a telescope for tracking celestial objects, an equatorial mount
must be aligned to the North Star. Once a target is found it can
be easily tracked in one axis with either slow-motion controls or
a clock drive. This avoids the sort of "View-and-Bump" method used
to track celestial objects with non-computerized alt-azimuth mounts.
Equatorial mounts are also ideal for long-exposure astronomical
photos. Since the mount is driven in only one axis to follow the
stars there is no "field rotation" in a long-exposure astronomical
photo.
There are two ways equatorially mount a telescope: Using a German
equatorial mount or a fork mount attached to a wedge plate.
Computerized Mounts 
Computerized mounts are usually alt-azimuth mounts. Computerized
mounts, after properly synchronized with the sky, can find and track
astronomical targets. Computerized system can also be controlled
from external computers like laptops.
For astrophotography the mount must be equatorially aligned to
prevent "field rotation" during a long exposure. This can be achieve
with a German Equatorial computerized mount, by using a wedge plate
with an alta-azimuth computer mount or a field-de-rotator on the
camera interface.
For any computerized telescope to properly work, you will need
to perform a "two-star" alignment before each observing session
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