Depression is not a single disorder. It primarily takes two forms: major depression and bipolar depression. Major depression, also known as unipolar depression, is characterized by persistent low moods. It impacts about 5% of the population and is a leading cause of disability. Bipolar depression, on the other hand, is characterized by manic highs, where people may exhibit behaviors such as not sleeping, talking very fast, and making impulsive decisions, followed by periods of low, lethargic moods. It's important to note that accurate diagnosis of these disorders should be done by a qualified healthcare professional.