Where can I find more information about the processes?
The related book
explains the definitions for the returns, volatilites and statistics used for the computations.
It presents in details the processes included in this site, from a broad structural overview to a detailled investigation of the most important processes.
While this site displays the statistics in a fairly raw form, the conclusions that can be inferred from this study are discussed in details in the book.
Furthermore, the implications for important practical applications like market risk evaluation, option pricing or multivariate extensions are discussed in specific chapters.