UPDATED 24/04/2021 8:10 AM
What is Bootstrap?
In 2010, Twitter needed a library in which the design includes uniform for different interfaces of web pages. From this idea, a framework was created in 2011, which was published as an open source project and is now widely used in its fifth version.
Bootstrap uses a superset of CSS, the stylesheet language Sass (Syntactically Awesome Stylesheets). Modular in design, Bootstrap 4 is divided into layout, content, bootstrap profile, components and tools. The developer can specify which components of these he wants to use.