Buried drusen is usually a congenital (you are born with it) abnormality of the optic nerve head, which is located in the back of your eye on the retina.

The optic nerve head is a very important place because this is where all the visual sensory information from your retina exit the eye via optic nerve fibers, and travel to the brain where the information is processed.

Some people have such mild buried drusen that it is either undetected or their vision is unaffected.

Some people may have more serious cases where parts of their visual field is missing (ie. blind spots larger than
normal).  In some cases, buried drusen progressively gets worse with age.

Rarely, buried drusen is associated with more serious disorders like retinitis pigmentosa or tumors of the optic nerve or optic nerve head.  These have potentially  more serious and devastating consequences to vision.
    
When eye doctors see buried drusen, they inspect the optic nerve head more closely because other much more vision threatening and even life threatening conditions can look similar to buried drusen, especially at a quick glance.  Currently there is no effective or proven way to treat progressive or severe drusen except to carefully monitor via yearly eye examinations.

Buried drusen is simply deposits of hyaline bodies (highly refractile calcium or other unknown material depsosits) that are found in and around the optic nerve head.  Some people develop drusen later in life as a result of other age related physiological changes in the eye.