This is something that I personally have been wondering about for a long time. I've known that RAID existed and generally what it does, but I really thought that it's more for servers and (since I don't have a ton of money to buy a ton of drives), I've never found the means to set one up.
But in any case, after watching his last video on "What Desktop Linux needs and its problems", I browsed some more of FearedBliss's videos and found one about this topic. It's really informative, but very easy to understand; I myself didn't know about LVM until watching this video. Check it.