How different CSS and Bootstrap on html?

Question

i think that css has basic rule and bootstrap has many different function than css

Answer 1

Bootstrap is simply a CSS library/framework created to help making responsive web pages easier. It's not a type of CSS, it's CSS that's already written and ready for you to use. All you need to learn is the class names.
https://www.w3schools.com/whatis/whatis_bootstrap.asp