Confusion exists in two major syndromes.
The acute syndrome, referred to as delirium, broadly corresponds to a transient, reversible, and functional, episode of cognitive impairment with no permanent structural alteration in the CNS.
The chronic syndrome, dementia, corresponds to a fixed or progressive neuroanatomical abnormality.
Note that confusion, delirium and dementia are descriptive terms. Confusion describes some form of disorientation, delirium a more specific type of acute toxic confusional syndrome and dementia a patient who appears to chronically have lost some form of higher mental function. Also note that not all people who seem to acutely confused have delirium, and not all those who appear chronically confused are confused at all.