Documentation on the arguments used when defining styles in an .inc file

I am new to using LyX, and recently asked a question about adding a modified style in an .inc file (Add caution and warning messages to book). One of the problems I had was finding documentation on the components or arguments of the modified style, such as Category, Margin, & LabelString. Is there a document or book where these are described? And what "language" are they in: LyX, LaTeX, or something else?

Thank you!