MOOCs or "Massive Open Online Courses" have mushroomed in recent years. These are online courses that you follow, with at your own pace or within a structure dictated by the supplier. MOOCs used to nearly all be free to follow but would (optional) invite you to pay to get a certificate at the end. Many still are, but you have to click in the right places on the screen to get access for a limitted time. Universities and employers are now very used to seeing these listed on CVs and often will not ask for proof of you having done the full course. Do give some thought to certification at the end and paying that one-off fee, as those same employers are now more than likely to ask for this as more people add MOOCs to their CVs. Do remember that falsifying anything on an application form (and your CV would constitute part of an application form) is a criminal offence - best to do the MOOC and think about paying for the certificate at the end.
MOOCs are rather like Internships and Work Experience; they show an employer that you are serious about your subject area and have the "stickability" to keep developing yourself.
For more on MOOCs try this page from "Save the Student", an independent UK site, set up by students and aimed at giving them the best advice.
A not-for-profit provider created by MIT and Harvard University, with around 20 million users and over 1,000 courses.