When you download Bootstrap, You can find there below system structure

bootstrap/ <!-- This is main bootstrap folder -->

├── css/ <!-- This is main CSS Folder -->

│   ├── bootstrap.css <!-- This is main Boostrap CSS Unminify file -->

│   ├── bootstrap.css.map

│   ├── bootstrap.min.css <!-- This is main Boostrap CSS Minify file -->

│   ├── bootstrap.min.css.map

│   ├── bootstrap-theme.css

│   ├── bootstrap-theme.css.map

│   ├── bootstrap-theme.min.css

│   └── bootstrap-theme.min.css.map

├── js/ <!-- This is main JS Folder -->

│   ├── bootstrap.js <!-- This is main Boostrap JS Unminify file -->

│   └── bootstrap.min.js <!-- This is main Boostrap JS Minify file -->

└── fonts/ <!-- This is Bootstrap Fonts Folder -->

    ├── glyphicons-halflings-regular.eot

    ├── glyphicons-halflings-regular.svg

    ├── glyphicons-halflings-regular.ttf

    ├── glyphicons-halflings-regular.woff

    └── glyphicons-halflings-regular.woff2

Note All Bootstrap package required jQuery file. You should it download or use CDN file link.

Bootstrap source code

The Bootstrap downloaded source code includes the precompiled CSS, JavaScript, and font assets, along with source Less, JavaScript, and others documentation. More specifically, it includes the following and more:

bootstrap/

├── less/

├── js/

├── fonts/

├── dist/

│   ├── css/

│   ├── js/

│   └── fonts/

└── docs/

    └── examples/

The less/, js/, and fonts/ are the source code for our CSS, JS, and icon fonts (respectively). The dist/ folder includes everything listed in the precompiled download section above. The docs/ folder includes the source code for our documentation, and examples/ of Bootstrap usage. Beyond that, any other included file provides support for packages, license information, and development. (Provided by Bootstrap)