Once upon a time there were MOOCs. They popped up out of nowhere (although in one guise or another they've been around as long as the web got its 2) and took the educational world by storm, but is the market now saturated with these and why are so many of them offered at a price? If you want to put them into a simple category you could start with those that are free and those that are not.
Paid MOOCs could then be simply classified into two simple categories again; those that are all about Learning - and those that are all about Earning. There's only a letter of difference but it makes a world of difference. If you're starting out looking at MOOCs the first piece of advice would be to not pay for it. Does this guarantee it's any good? No, and nor is the converse true, it just means that so many of us don't know what we don't know, yet still insist on picking what someone else insists is something worthwhile. What I mean simply is if you've never 'done' a MOOC before then do a free one first and see how you go. Paid MOOCs aren't a bad idea, after all if you want world-class training there's a fair chance that you will have to pay for it; just be aware paying for it doesn't guarantee that. On the other hand it often means that someone has done some sort of quality check on it that may not occur for a freebie.
Free MOOCs aren't hard to find but the key here is that just as necessity is the mother of invention, having some need to learn a specific something should be your motivator. Yes, you can take a course on 'anything' but you'll only learn about 'anything' - not much use if you wanted to learn about 'something' or even 'something else'. If you're after just a little bit of knowledge then a MOOC may not be for you at all... Google will probably find the answer if you have a simple question or a few questions. You have to remember that MOOCs have their grounding in higher education so you can expect quite an academic or educational approach to learning rather than a training approach.
Where to go? The first MOOC provider (and credited by most as the inventor of the MOOC) is Coursera - not a bad place to start either as all the courses are free! You can also try edX which is quite similar or Udemy which has quite a range of often more professional looking courses - but watch as there is a mixup of paid and free courses on the site. If you don't want to get involved in the 'community' side of things, you'll probably find again that the MOOC may not be for you - you can find courses that are designed for a single user without interaction, but you've probably found just an online textbook of sorts (yes, even if it's video) and may have missed the social bus.
Long and short of it is that whilst I may go Google something, going to MOOC it didn't ought to slip into our vocabulary any time soon - it's a commitment to a level of learning and involvement. Statistics show us that less than 10% of MOOCs are completed...
One last thing to watch for; lots of MOOCs have a time commitment and weekly exercises and things that require you to be active. Whilst there are launch and track type MOOCs that you can meander through at your own pace, lots will just leave you behind and you'll not get anything out of them. If they say they require you to spend a few hours a week on them, make sure you can actually commit the time, otherwise you'll fall into the 90% from the aforementioned paragraph!
If I've put you off I don't mean to. MOOCs are a great concept and really good at delivering some high-level learning if done right, they are just not the be all and end all of 'learning'. Be careful with your time and your money and research your subject and time commitments before embarking.
Can I recommend some good ones? Yes, but DM me as what's good for the goose...