Shortcodes as they are implemented in Elder.js (what the article is about) are borrowed from WordPress. Basically they are a placeholder such as [[lastestTweet/

Shortcodes as they are implemented in Elder.js (what the article is about) are borrowed from WordPress. Basically they are a placeholder such as [[lastestTweet/]] that let you add dynamic content into otherwise static content. While Elder.js does allow for full server side rendering making "Javascript the backend" the goal of the static site generator is generate static HTML/CSS/JS that can be hosted from a CDN, S3, or other static host. That said, one of the biggest pitfalls with building a major site on a static site generator is there is often no upgrade path to server rendering. Elder.js does offer that out of the box.