Informal learning, in contrast with formal learning, occurs outside formal classroom settings and is not part of a school program, activity, or assignment. Informal learning is voluntary, self-directed, lifelong, and motivated mainly by intrinsic interests, curiosity, exploration, fantasy, task completion, and social interaction. Informal learning can be linear or non-linear and often is self-paced and visual- or object-oriented. It provides an experiential base and motivation for further activity and learning. The outcomes of an informal learning experience in science, mathematics, and technology (SMT) include a better understanding of concepts, topics, processes, and thinking in scientific and technical disciplines, as well as increased knowledge about career opportunities in those fields. While ISE projects are aimed primarily at the informal learner, the ISE program encourages linkages to formal education.

from Elementary, Secondary, and Informal Education Program Solicitation and Guidelines, National Science Foundation, 2001