Of late, grid systems have been extensively used in web-development workflows. Grid systems aim to streamline the HTML markup process by providing a standard set of dimensions and display styles for the commonly used UI elements. The following screenshot shows a grid system:
Bootstrap has a default 12-column grid system that is available as a responsive, fluid, and fixed layout. It comes with a complete set of predefined classes that meets nearly all your UI styling needs.
Some of the most commonly used classes are mentioned in the following table: