It can be configured to work almost like how you would expect a typical CMS to work – with different content types, additional fields in the forms etc: https://github.com/prose/prose/wiki/Prose-Configuration Which means users don't have to know much about Jekyll to add content to such a site.

Prose is tweaked specifically to offer additional features to sites built with Jekyll.

They have a markdown editor, similar to the one github offers, but have a few extra features to deal with Jekyll specific stuff like drafts, image uploading and a distraction free writing mode.