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.

Hugo is an open-source static site generator that features fast build times, flexible themes, support for multiple content formats, multilingual websites, live reloading, and an active community. It allows developers to easily create and deploy SEO-friendly and mobile-responsive websites.

Jekyll is a static site generator written in Ruby that allows you to create simple, fast, and secure websites without the need for a database.

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.

Netlify is a cloud-based web development platform that provides a range of tools and services to help developers build, deploy, and manage modern web applications. It offers features such as continuous deployment, serverless functions, and CDN hosting, making it an ideal platform for building fast, scalable, and secure websites.