This is an introduction to Bootstrap. You need to know how web pages work, but that's about it. It's not anything super advanced, just a "get 'er done" version. You can find way more on the interwebs and the Bootstrap site.
You probably also want a text editor, like WebStorm, Sublime, Notepad++, Brackets, or just use vim or emacs. Whatever floats your fancy. Oh, and a browser (don't argue, and just use Chrome). Before you get too deep into Bootstrap, you might want to learn Chrome Developer Tools for Chrome or Firebug for Firefox, just to make debugging and experimentation even easier!
Sure enough! Visit this page to more Bootstrap examples and add-ons. Want to use Bootstrap in a Java project? Easy as pie! Check out some examples: