Distant learning, also known as distance education, e-learning, and online learning, is a type of education in which teachers and students are physically separated during instruction and various technologies are used to allow student-teacher and student-student communication. Distance learning has generally targeted nontraditional students, such as full-time workers, military people, nonresidents, or persons in remote areas who are unable to attend classroom lectures. Distance learning, on the other hand, has become an established component of the educational sector, with trends indicating continued expansion. In the fall of 2009, more than 5.6 million university students in the United States were enrolled in at least one online course, up from 1.6 million in 2002.