Bootstrap is a free compilation of website and web apps creating tools. It consists of intuitively designed templates based on HTML and CSS for typography, forms, buttons,
navigation etc. It also has optional extensions of JavaScript. To know more about Bootstrap, read this article!
From entirely CSS-driven style sheets to a powerful, mobile-first, responsive, front-end framework with lots of new features added including host of JavaScript plugins, tools and icons that go hand in hand with forms and some more components, it's safe to say that Bootstrap has come a long way.