Bootstrap is a popular front-end framework used for designing websites and web applications. It provides a collection of pre-designed HTML, CSS, and JavaScript components that help developers create responsive and visually appealing layouts quickly. By using Bootstrap, developers can ensure their websites look good on various devices, from smartphones to desktops. The framework was originally created by Twitter developers Mark Otto and Jacob Thornton in 2011. It has since become widely adopted due to its ease of use and extensive documentation. Bootstrap also supports customization, allowing developers to modify its components to fit their specific design needs.