Online learning has been used over the past decade in most disciplines at higher education while the asynchronous online courses are one of the more popular modes of conducting online learning. Within the asynchronous online course, the asynchronous discussion forum plays an important role since it can replace the face to face interaction of the traditional classroom. Since discussions are critical in any learning process, the question is what are the essential components of the asynchronous discussion forum that can make asynchronous discussions more effective for learning and knowledge construction? This paper reviews the literature regarding the main elements and components that makes an asynchronous discussion forum more effective for knowledge acquisition and thereby increases the quality of online learning.