This example is a minimal setup that lets you use JSON files (in _data/) as collections of data and Nunjucks templating engine to display that data on a website.
Install with npm install and run with npx @11ty/eleventy --serve to start a dev server and npx @11ty/eleventy to build into _site that can be deployed to a server.
Anything stored in assets/ folder will be copied as-is into _site/assets and not processed. To link to those in your templates or HTML, you can use {{ '/assets/main.css' | url }} that generates correct URLs (replace main.css with your filename).