GatsbyJS is a free and open-source static site generator based on React. It uses a modern development stack including Webpack, GraphQL, and modern JavaScript and CSS frameworks. It also provides a rich set of plugins, starters, and themes.

React is a widely used JavaScript library for building user interfaces and single-page applications. It follows a component-based architecture and uses a virtual DOM to efficiently update and render UI components

Bootstrap is the most popular CSS Framework for developing responsive and mobile-first websites.