If you don’t know Sapper: It’s very similar to Nuxt or Next.js with the additional option to even export as static html, so the end result is similar to a Gatsby website.

The folks at Netlify created Netlify CMS to fill a gap in the static site generation pipeline. There were some great proprietary headless CMS options, but no real contenders that were open source and extensible—that could turn into a community-built ecosystem like WordPress or Drupal. For that reason, Netlify CMS is made to be community-driven, and has never been locked to the Netlify platform (despite the name).

They might be built using sites built by hand, or with Jekyll, Hugo, Nuxt, Next, Gatsby, or another static site generator...