Dust JS is a JavaScript templating engine that separates presentation from logic. It allows for cleaner coding through logic-less templates and features like blocks, partials, and helpers. Dust runs on both client-side and server-side. Popular companies like LinkedIn and PayPal use Dust due to its active development, battle testing, and community support. Dust's data referencing allows accessing data outside of loops through features like {@eq} and {@size}. Templates are populated with JSON data through a three step process: 1) Dust templates for markup, 2) JSON data, 3) JavaScript rendering engine.