Today, most websites are becoming responsive. Responsiveness is the most requested option when coming to websites front end development. This option makes websites mobile friendly with most modern web browsers.
Bootstrap is one of the most popular frameworks for developing responsive, mobile first projects  on the web. It’s made for folks of all skills, levels, devices of all shapes and projects of all sizes.
Bootstrap is open source. It utilizes the two most popular CSS preprocessors, Less and Saas.
Wide Range of Responsive Components
Bootstrap has a wide range of components. Bootstrap components are for all types of usage including button dropdowns, panels, buttons, input groups, labels, pagination, …, etc.
It is also bundled with Glyphicons iconic font library to make components easier to understand and maintain. Developers also integrates the Bootstrap Library with FontAwesome library to make professional websites.
Modern Themes Support Bootstrap
Today’s trend is to support bootstrap. Many themes support Bootstrap including HTML and WordPress Themes.A new trend called HTML Builders have integrated Bootstrap as the main CSS framework.