Themes folder

Themes folder

Your default stylesheet files and images are stored in themes folder.
Themes folder can also contain custom theme set you made.
For example if you are developing theme set for your site, you can create new folder (i.e. my_site_theme) and copy entire content of default folder inside.
You can choose your template set from administration >> preferences >> General options >> Choose theme option.

default:
css - contains default stylesheets for Vivvo frontend
img - contains default images for Vivvo frontend