The theory used to teach adults is called andragogy or adult learning theory. Adult learning theory has some recurrent themes that can be summarized into three key points:
1) An adult learner’s self-concept and individuality are paramount to the learning process. The principles of personal experience, readiness to learn, and motivation to learn all reflect this. External factors hold little value, but individual development remains a consistent topic.
2) Adult learners want to learn to do.
3) Adult learners always have clear reasons for learning.