This is a brilliant little video from a retired Microsoft engineer who worked on Windows, so knows a thing or two. It's less than 15 minutes long, but does explain a lot. And an update with more information.
What is Bitlocker? It's a drive encryption program that makes the data on your drive 'secure'. Is it good? Yes, and no. Yes because your data is more secure, however unless you have the recovery key, you won't be able to access your data - even taking the drive out of your PC and connecting it to another one won't be able to get your data off. How do I keep my recovery key safe? Ideally, Microsoft would like you to keep the recovery key linked to your Microsoft Account. This is all well and good if you have (or want) a Microsoft account, but not everyone wants one. You can store a file on your PC with the recovery key, but this is NOT recommended as if you ever are unable to boot your computer and access the drive then you are not going to able to get to the file! You can write down the recovery key, but if you do this, store it somewhere safe. You can store the file on a USB pen drive. Again store this safely as if you loose it, you'll not be able to access the