Informal learning is, by default, any learning that is not formal learning or non-formal learning. Informal learning is organized differently than formal and non-formal learning because it has no set objective in terms of learning outcomes and is never intentional from the learner’s standpoint. Often, it is referred to as learning by experience or just as experience. For all learners this includes heuristic language building, socialization, inculturation, and play. Informal learning is a pervasive ongoing phenomenon of learning via participation or learning via knowledge creation, in contrast with the traditional view of teacher-centered learning via knowledge acquisition. The term is often conflated, however, with non-formal learning, and self-directed learning. It is widely used in the context of corporate training and education in relation to return on investment (ROI), or return on learning (ROL). It is also widely used when referring to science education, in relation to citizen science, or informal science education. The conflated meaning of informal and non-formal learning explicates mechanisms of learning that organically occur outside the realm of traditional instructor-led programs, e.g., reading self-selected books, participating in self-study programs, Kitchen Table science, navigating performance support materials and systems, incidental skills practice, receptivity of coaching or mentoring, seeking advice from peers, or participation in communities of practice, to name a few. Informal learning occurs in community, where individuals have opportunities to observe and participate in social activities.