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

Styled Components is a popular library for styling React components using CSS syntax. It allows you to write CSS in your JavaScript code, making it easier to create dynamic styles that are specific to each component.

A template or theme refers to a pre-designed layout or structure that provides a basic framework for building a specific type of application or website. It typically includes good design, placeholder content and functional features, allowing developers to customize and fill in the details according to their specific needs.