Cognitive-behavioral theory emphasizes the cognitions or thoughts a person has as an explanation as to how people develop and how they sometimes get a mental disorder. Many types of theories in psychology could fit under this broad category, and it would be difficult to do them all justice, so I'm just going to focus on some of general points of them all. Cognitive-behaviorists generally believe in the role of social learning in childhood development, and the ideas of modeling and reinforcement. So, in other words, if your parents act like snooty, uptight individuals all their lives, and treat other people with little dignity or respect, you, as a child, would learn to do much of the same thing. If your parents don't cry when they're emotional, you may also learn to hide your feelings and not cry when you're emotional.
Children learn by observing and imitating.
This is social learning theory. There's also a lot of discussion about how a human's innate drives and habits affect all of this, but we won't get into all that. Save to say that there is such a belief that it is these innate drives which underlie the motivation of human behavior. If you grow up in a maladaptive or unhealthy environment, or you don't learn, for whatever reasons, proper coping skills, you can have mental disorder problems later on in life. Despite the negative-soundingness of this, the fact is that in this theory, humans are viewed as basically neutral.