In simple terms, an online course is one that is offered entirely online, via the Web and its associated technologies. A hybrid course is an optimal blend of online and offline components. Many different versions of the hybrid course exist, with different types falling along a continuum with the fully online class defining one end of the spectrum and the traditional classroom on the other. A few examples along this continuum can help to illuminate their differences.
The Online Class
An online class is offered entirely online. If a learning management system is used, students log in through a Web interface to access the course structure, syllabus, discussion board, assignments and other course materials. Synchronous activities might include live chats or video conferencing. Communications with an online class professor may include the more traditional methods such as phone calls or emails, along with office hours via a live chat or webcam session. While face-to-face meetings aren't always eliminated from the online class -- a professor might welcome in-office meetings, or study groups may meet in person -- a truly online class is primarily conducted through the Internet.
The Flex Model
The flex model is one step away from the fully online course in that it offers regular classroom sessions that are attendance-optional. The teacher or teacher's assistants are available in the classroom on a regular schedule to assist those students who need or want face time. Sometimes even the classroom sessions are flexible, offered only as students request them. Another version of the flex model brings the students together when one of them is ready to present findings or the results of a project completed independently. These meetings are mandatory but irregular and more informal than a traditional class session.
The Flipped Classroom
The flipped classroom uses the Internet to deliver traditional instruction materials while reserving regular class time for problem solving and mastery-type activities. This makes more efficient use of face time between teacher and classmates. Students access archived audio or video lecture sections online after hours, learning at their own pace, with the option to view and review the material as necessary. Virtual discussions of the material occur via a chat room, discussion board or even Twitter. During class time, classmates work out problems together or consult the teacher for additional insights on the subject.
The Online Lab
The online lab takes place in a traditional classroom or computer lab environment, but the actual learning is done through a Web interface. In some cases, the online lab is just one component of an otherwise traditional class, supplementing or enriching the traditional class lessons with online activities. In other cases, the students regularly meet and log into an online interface, with the majority of course work completed through the Web.