This is just testing Nuxt.js application's feature. Thus, backend is relying on Firebase. A layout of this architecture is below(very simple though).
# install dependencies
$ npm install # Or yarn install
# serve with hot reload at localhost:3000
$ npm run dev
# build for production and launch server
$ npm run build
$ npm start
# generate static project
$ npm run generate
For detailed explanation on how things work, checkout the Nuxt.js docs.