The term Computer Based Exam (or Computer Based Test) encompasses online-exam. Online-exam may be considered as a sub-class of Computer Based Exam, wherein the exam is conducted online. Online is used in the sense that the computer being used to take the test is connected to the intranet or the Internet, in client-server environment. The computer being used for taking the test can be considered as a client computer. The server computer is the one that is sitting somewhere on the Internet (or the intranet) and delivering the exam. Usually, in an online exam, there is some form of communication between the server and the client (not necessarily continuous). The exam results are uploaded to the server computer after the exam. The role of the client ends after you finish the exam and the results are uploaded. In technical terms, the session ends after the exam is completed.
Now, coming back to Computer Based Exam, as was mentioned earlier, is a generic term used for any kind of exam or test given on a computer. The computer may or may not be online. In other words, may or may not have been connected to a server on the Internet (or intranet).
After giving the exam in a CBE or CBT (short forms for Computer Based Exam and Computer Based Test), the results may be stored locally on the computer hard-disk or transported online to the web server. Usually, stand alone testing is referred to as CBT.
Competitive exam are often referred to as Online Exams because they are delivered in real time simultaneously over the network to several students and the exam is conducted in client-server environment.
An example of CBT may be viewed CBT Software-Exam Engine. Here a candidate downloads the CBT software from the Internet and installs it on his/her own computer and uses the exams. There is no server connection required for taking the quiz.