Hey, sorry for the lack of details. We're still working on that.
Basically, Postach.io looks in a notebook you specify when creating a site, for notes that are tagged as "published". This will make a post on your public site. Any images are pushed to our CDN. If a note is tagged with "page" as well as "published" its made public as a page. When a note is deleted or the tag "published" removed, it will be removed form your public site as well as any images from our CDN.
Basically, Postach.io looks in a notebook you specify when creating a site, for notes that are tagged as "published". This will make a post on your public site. Any images are pushed to our CDN. If a note is tagged with "page" as well as "published" its made public as a page. When a note is deleted or the tag "published" removed, it will be removed form your public site as well as any images from our CDN.
Hope that answers your questions ;)