JAMStack is a new approach to website development that uses client-side JavaScript, reusable APIs, and prebuilt Markup. It allows developers to build incredibly fast and secure sites without traditional server-side dependencies. Key benefits of JAMStack include speed, security, scalability since sites are static and cacheable. Content is fetched and sites are built ahead of time during the static site generation process and then deployed to CDNs for fast global delivery without server processing.