These are general description of Mood Disorders that does not include all of the diagnostic criteria but is intended to give you a glimpse at the disorder. For a fuller description check the Mood Disorder at the National Institute for Mental Health.
http://www.nimh.nih.gov/publicat/depression.cfm
A mood disorder is a disturbance of the emotions or of the way you feel.

A Major Depressive Disorder is one in which there is a depressed mood in which the person is very sad or irritable and no longer gets pleasure from activities that they once enjoyed. There is likely a loss of interest in almost everything. Decreased energy, loss of sleep and or appetite and difficulty in thinking, making decisions, reoccuring thoughts of death or suicide as well as feeling worthless, helpless and hopeless. A specified number of symptoms must have been present for most of the day for two weeks and must have been associated with significant problems in social, occupational and other areas of functioning.

Other Mood Disorders are:

Dysthymic Disorder- two years of depressed mood plus other symptoms
Depressive Disorder Not Otherwise Specified (NOS) does not meet the criteria for other related disorders.

Bipolar Disorder 1

Bipolar Disorder 11

Cyclothymic Disorder

Bipolar Disorder NOS

Mood Disorder due to a General Medical Condition

Substance Abuse Induced Disorder and Mood Disorder NOS

Effective medical treatment of mood disorders and anxiety disorders by using psytropic medication has been called into serious question by a recent study (clock news button)in which the effect of psychotropic medication such as Zoloft and Prozac proved to help only 50% of people under extraordinarily supportive medical service. The researchers stayed in contact with the studies subjects and spent more time than is usually spent with patients checking their symptoms and adjusting their dosage sometimes on a more than weekly basis. Without that exceptional follow-up, it is estimated that less than 10% of patients would have been helped (see news – this website)