When to use Twitter Bootstrap and when to HTML5 Boilerplate?

I am pretty bad with CSS and HTML5 designing/templates. So, I google around and found two frameworks to start with nice looking layouts, necessary js and html5 support. But I don't know which on to use. I would appreciate your answers on What is the main different between two except google analytics ? Which one is more rails friendly ? - Which one fits best to e-commerce sites, i.e. create rich content, integrate with user management frameworks etc?