The Strong is based on the vocational theories of John Holland. Holland suggested six personality types and six work environments: Realistic, Investigative, Artistic, Social, Enterprising, and Conventional. These personality types result from an interaction among culture, heredity, social status, education, peers, parents, and the physical environment. From experience, people learn that they like some activities more than others. Oftentimes, competency results from engaging in the same activities repeatedly. As these competencies grow, the person tends to think, act, and perceive in special ways.
So those who are Artistic types tend to seek out occupations that encompass the Artistic aspects of a job, or jobs that are by nature Artistic. In turn, they are likely to seek out environments that support their interests and abilities. These work environments are likely to be populated with others who share similar interests. This cycle perpetuates itself: the environment attracts certain types, who shape the environment to their liking, which in turns tends to attract those who enjoy the same things. The people in the environment tend to shape that work environment. Artistic work environments are dominated by Artistic types. Conversely, people tend to avoid those situations and environments that conflict with or are different from their preferences. For example, Artistic types are less likely to enjoy working in a Conventional job, such as Bookkeeper.
The Strong Interest Inventory works by measuring the interests of people who enjoy their work, have been in the field at least three years, and who do typical work for the field. When you take the Strong, your responses are compared to the representative sample of these occupations. You can have similarities with few or many occupations. An important aspect of finding a good career fit is that when you have a person-environment match, you're probably going to use your skills and abilities, take on agreeable problems and roles, and be able to express your attitudes and values. People search out those environments that match their interests. The environment attracts people through recruiting efforts and friendships with those already working there. This is a long-term process, taking place over many years.
Congruence simply means you're in an environment that matches your interests. If you're an Artistic type, you're in an Artistic environment. This is important because Artistic environments provide opportunities and rewards that Artistic types need and want. Obviously, an Artistic person in a Conventional environment will be less likely to find the work rewarding, enjoy the tasks or the people involved, or like being there. The greater the person-environment match, the more likely the person will be satisfied doing that kind of work.