It's a flavor of planitjs for processing guitar tab plan files.
First argument is the name of the tablature.
A group of notes played together is defined as one step. Each line represents each step.
To define a note, just state the string and fret number.
For example, g string 14th fret is a note.
If you want to bunch up multiple notes into one step, join them up using commas in a single line.
For example, eh string 2nd fret, g string 2nd fret, b string 3rd fret has 3 notes are grouped into one step. In this case, it's a D chord and the notes are supposed to be played together in a single step.
Unnecessary whitespaces are ignored. Feel free to use them for organizing your content and making them look good.