Also known as: CMS sites, Self-managed or Self-maintained sites.
CMS is web jargon meaning Content Management System. Essentially a CMS website is one where you the client can update the content of the site yourself, without knowing any fancy code or owning extra software packages.
If your site requires frequent updates to images or text content
If your site carries large amounts of content
If you want to update and maintain your site yourself
If you want other people to contribute to your site