Bipolar Disorder used to be known as Manic-Depressive Disorder, a name that described the two polar opposite manifestations of the illness: a depressive stage which is either preceded or followed by a manic, hyperactive stage.  The new name for this serious mental health condition reflects the bipolarity (cycling through) of the symptoms, that is, the radically different emotions that can be experienced and the contradictory behaviors that can be exhibited by the same individual.  It is a disorder that requires specialized treatment, often with a combination of psychotherapy (primarily cognitive-behavioral therapy) and appropriate medication.