For all of you wondering what those words mean on this website, here is the answer. I separate the levels by technique. Basic means that you can blow and draw all the notes, but don't know how to bend. In the category I also include the most basic lessons on playing the harmonica, but some of the tunes are not totally simple- they just don't have any bends.
Intermediate level includes bending, so this is where really playing Blues starts, as well as just being able to get a lot of the notes that you can't get by regular blowing and drawing. This level has more advanced lessons and has many more tunes to learn.
The Advanced level introduces the player to the wonderful world of Overblows and Overdraws that enable a diatonic harmonica player to get all the notes, just like you can on every other instrument. If you learn how to do this, it opens up the instrument to endless possibilities. As a result, Advanced level includes every style of music, Jazz theory lessons, etc.
Virtuoso level is the same technical level as Advanced, except that the tunes on this level are more difficult to play. This is the smallest category, but it, like all the others, is constantly growing.
So find your level and explore it. After a while, many of you will start to advance to the next level. It gets to be more and more fun as you do this. Happy Hunting!