The major difference between the two lies in the fact that while Bootstrap is a front-end framework, CSS is a style sheet language. Other differences include: Bootstrap provides a systematic grid system to place the content while CSS doesn’t. Bootstrap contains already designed classes to let programmers add styling to the elements without writing the code whereas CSS requires a programmer to write code from the scratch. Bootstrap contains more features as compared to CSS. Bootstrap is responsible for creating presentable and responsive designs while CSS allows us to create presentable webpages.