Several. Major depressive, bipolar i, bipolar ii, dysthymic, and cyclothymic disorders are the basic ones. Each can have special 'features' that change their appearance in individuals. The mood disorders have to do with a mis-regulation (unusually high, irritable, and/or down) of the person's longer-term emotional states or moods (though sometimes moods can rapidly cycle).
Several. There are two basic mood disorders, unipolar depression and bipolar disorder. In unipolar depression, patients do not become manic or hypomanic and in bipolar disorder, although people can become manic, they are usually depressed. That being said, here is a partial list of mood disorders: mood disorder related to substance abuse, mood disorder related to a medical illness, dysthymia, cyclothymia.