The online world has given us all a lot of great things. You can check out more, research more, work more, play more and meet more new people than you would ever have had the opportunity to in any previous generation. The world is just that much better than it has ever been before, and we are all the beneficiaries of this sweeping (and thoroughly swept through) change. Of course, nobody is guaranteed anything, even when they are online. You are not guaranteed to extract any benefits which you do not work toward gaining. So if you want to learn something online, you are going to be limited if you expect the osmosis effect, where you just gain knowledge from being in its presence. When it comes to learning things online, especially involving doing research, you are solely the master or mistress of your own destiny.
First off, keep in mind that while there is a lot of great content online, there is also a lot of filler content and fluff. While such things might be entertaining to read, these types of sources are not the most effective method of actually gaining and retaining knowledge. Online schools typically will not refer you to fluffy or redundant sources, but they are fairly abundant online no matter where you go. Just be warned about their presence, and keep yourself at a safe distance from them, so that you do not fall into the trap of thinking you are getting smarter while you sit there staring at something useless.
Also, once you have a good search query (a few solid questions) on a topic, you are going to have to actually work to understand what you take in. While looking at something which came up on a search query might look like you are learning something, try to remember it five minutes later. If you have a lot of trouble doingso, it is still not very well internalized in your mind. One good way to remember things of a complicated nature is to try to visualize them, and then pretend you’re teaching it.