what is the difference between bootstrap.min.css and bootstrap.min.js?

Question

what is the difference between bootstrap.min.css and bootstrap.min.js ? Why bootstrap.min.js need to be included?

<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">

and

<script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>

Answer 1

They're both minified versions of the complete Bootstrap style (CSS) and components (JS). You don't need to include the JS to use the Bootstrap styles (responsive grid, buttons, tables, typography, panels, etc..).

However, you do need to include the JS if you want to use the Bootstrap JavaScript components (modal, carousel, data-attributes, scrollspy, tooltop, etc..).

Answer 2

Bootstrap.min.css contains the CSS necessary for the Bootstrap to work correctly.

Some of the functionality offered by the bootstrap aren't possible though using only plain .css and this is where javascript comes into play.

Bootstrap.min.js contains javascript code necessary for running Bootstrap.