For the first insertion of a website photos and videos configurations won't have any value. You will have to insert them. For the next times, it will be filled with the values of your last insertion.
DOMAIN & SUBDOMAINS
The url where the new website will be.
- Static files subdomain
Where static files, like CSS, JS, JPGs and other files will be.
Why? To allow some web performance technics with Apache or nginx and easly deploy it on CDN.