Bootstrap has become one of the most popular front-end frameworks and open source projects in the world.
(Sourced from the official repository readme.md)
Within the download you'll find the following directories and files, logically grouping common assets and providing both compiled and minified variations. You'll see something like this:
bootstrap/ ├── css/ │ ├── bootstrap.css │ ├── bootstrap.min.css │ ├── bootstrap-theme.css │ └── bootstrap-theme.min.css ├── js/ │ ├── bootstrap.js │ └── bootstrap.min.js └── fonts/ ├── glyphicons-halflings-regular.eot ├── glyphicons-halflings-regular.svg ├── glyphicons-halflings-regular.ttf └── glyphicons-halflings-regular.woff