edXThe verified certificate, signed by the instructor and bearing the institution's logo, gives you the ability to highlight your new skills and knowledge on your resume or LinkedIn profile, plus gives you some extra incentive to finish the course. The certificate fee, which can cost $40 to $160 depending on the course, also helps support edX as a non-profit.
If you choose to audit the course for free, you still get complete access to all the course materials, activities, tests, and forums.