The American Psychological Association (APA) provides extensive materials on careers in psychology and related fields.  Here is a brief excerpt from APA's overview: 

"Psychology is a tremendously varied field. Psychologists conduct both basic and applied research, serve as consultants to communities and organizations, diagnose and treat people, and teach future psychologists and those who will pursue other disciplines. They test intelligence and personality. Many psychologists work as health care providers. They assess behavioral and mental function and well-being, study how human beings relate to each other and also to machines, and work to improve these relationships. And because the United States is undergoing sizable change in its population makeup, psychologists provide important knowledge and skills to help better understand diverse cultures..."

"Psychologists traditionally study both normal and abnormal functioning and treat individuals with mental and emotional problems. They also concentrate on behaviors that affect the mental and emotional health and mental functioning of healthy human beings. For example, psychologists work with patients to help them change behaviors that are having negative effects on their physical health. They work with business executives, performers, and athletes to reduce stress and improve performance. They advise lawyers on jury selection and collaborate with educators on school reform. Immediately following a disaster, such as a plane crash or bombing, psychologists help victims and bystanders recover from the trauma, or shock, of the event. They team with law enforcement and public health officials to analyze the causes of such events and prevent their recurrence. Involved in all aspects of our fast-paced world, psychologists must keep up with what’s happening all around us. When you’re a psychologist, your education never ends..."

"In addition, an aging America is leading to more research and practice in adapting our homes and workplaces for older people. The promises of the electronic revolution demand more user-friendly technologies and training. More two-career families in the workplace spur employers to accommodate the needs of families. Psychologists are helping to make the changes that are needed. The diversity in America today calls for psychologists to develop and refine treatments and approaches to meet the unique needs of different racial and ethnic groups. Furthermore, research advances in learning and memory, and the integration of physical and mental health care, make psychology more exciting than ever."