The courses primarily concern the studies of songs. These studies are ordered by categories related to the playing techniques used : Arpeggios, Strumming, Flatpicking, Fingerstyle, Plucking, Picking, Bossa/jazz and No barre chords. To have an overview of all the online studies of songs, go to Studies. If you are just beginning to play, go to Beginners where are all the level 1 and level 2 courses. In Basics are grouped all the theory courses from the “Beginners Guitar Lessons” series.
Because I am not a native english speaker, I have certainly made some wrong translations, please don’t hesitate to correct me if you are familiar with the guitar terms and vocabulary