Templates folder explanation

Templates folder

Templates are fragments of xHTML code interspersed with VTE language variables. Combined together they form complete xHTML pages that are served up to visitors.
Your default templates are stored in xhtml folder.
Templates folder can also contain custom template set you made.
For example if you are developing set of templates for your site, you can create new folder (i.e. my_site) and copy entire content of xhtml folder inside.
You can choose your template set from administration >> preferences >> General options >> Template folder option.

xhtml:
archive - contains main templates for archive view
article - contains main templates for article view
author - contains main templates for author view
box - contains reusable box templates
category - contains main templates for category view
frame - contains reusable frame templates
homepage - contains main templates for home page view
plugin - contains plug-in related templates
search_results - contains main templates for search results view
summary - contains reusable short article templates
system - contains system templates
box_default - default Vivvo modules templates
tag - contains main templates for tag view