It’s very similar way of earning money online to being online consultant – it’s basing on your (or someone else, who prepaid excellent material for your site) reputation and knowledge.
But as opposed to be online consultant, you share your knowledge and experience with more than one man at one time. What’s more, you produce almost all material for your members before starting this type of website.
Of course there are a lot of other differences – most important of them is price! Fees for accessing membership site are almost always fewer, than fees for hiring online consultant. And for this reason, membership sites must have many more customers, than online consultants