A model is a theoretical way to understand a concept or an idea. There are several models of health promotion and illness prevention. First, is the health belief model, or HBM, which predicts health-related behaviors regarding specific health belief patterns. In HBM, a person's motivation to participate in healthy behaviors is classified into three components: The first component of this model is a person's perception of their vulnerability to disease. The second component is a person's perceived seriousness regarding the threat of disease and its effect on their lifestyle. The third component is a person's perception of the benefits and impediments to adopting preventative action. Next is the health promotion model, or HPM. It states that individuals seek to interact with the environment, progressively transforming it and being transformed by it over time. The HPM model comprises three components. Individual characteristics and experiences predict an individual's health-related behavior. Behavior-specific knowledge anticipates positive outcomes from a particular health behavior. Lastly, behavioral outcomes focus on improved health and quality of life at all stages of development.