Historically, Distance Education meant correspondence study. Today, audio, video, and computer technologies are more common delivery modes. The separation of teacher and learner during at least a majority of each instructional process. The use of educational media to unite teacher and learner and carry course content. There are two categories of distance education delivery systems, synchronous and asynchronous.
Synchronous instruction requires the simultaneous participation of all students and instructors.
Asynchronous instruction does not require the simultaneous participation of all students and instructors. Students do not need to be gathered together in the same location at the same time. Rather, students may choose their own instructional time frame and gather learning materials according to their schedules. Asynchronous instruction is more flexible than synchronous instruction. Moreover, in the case of telecommunications such as email, asynchronous instruction allows and even may encourage community development.