Contemporary learning theories emphasize the importance of active learning, in which learners are viewed as agents who actively construct knowledge. In this perspective, learners have agency and must make decisions about their learning strategies, seek learning resources, and connect their new learning to their prior knowledge. Because of this agency, and the nature of free choice in out-of-school learning environments, participants may be described as learners, visitors, youth, citizens, or participants. Active learning may occur individually or it may occur collaboratively with peers or families or in collaboration with experts. Thus, the type of participation and how individuals are described will shift depending on the context of learning and roles of the learner. This entry discusses formal theories of learning related to active learning, informal ...