Bootstrap
Bootstrap is a free and open-source collection of tools for creating websites and web applications. It contains HTML- and CSS-based design templates for typography, forms, buttons, navigation and other interface components, as well as optional JavaScript extensions. It aims to ease the development of dynamic websites and web applications.
Bootstrap is a front end framework, that is, an interface for the user, unlike the server-side code which resides on the "back end" or server.
Projects of Bootstrap: