Yeoman is a tool for modern web development workflows that consists of three key components: Yo, Bower, and Grunt. Yo is a scaffolding tool that generates project structure and files. Bower is a package manager for front-end components. Grunt is a JavaScript task runner for automating development tasks like testing, building, and previewing projects. The document provides examples of using Yeoman, Bower, and Grunt together to generate the structure and dependencies for a sample Backbone application, add testing with Mocha, and build and preview the project.