A lesson or class is a structured period of time where learning is intended to occur. It involves one or more students (also called pupils or learners in some circumstances) being taught by a teacher or instructor. A lesson may be either one section of a textbook (which, apart from the printed page, can also include multimedia) or, more frequently, a short period of time during which learners are taught about a particular subject or taught how to perform a particular activity. Lessons are generally taught in a classroom but may instead take place in a situated learning environment.
In a wider sense, a lesson is an insight gained by a learner into previously unfamiliar subject-matter. Such a lesson can be either planned or accidental, enjoyable or painful. The colloquial phrase "to teach someone a lesson", means to punish or scold a person for a mistake they have made in order to ensure that they do not make the same mistake again.Lessons can also be made entertaining. When the term education is combined with entertainment, the term edutainment is coined.