Bootstrap is an extremely useful framework which can provide developers with a toolkit of useful components from Forms, Buttons, Styles, Icons, Typography, Responsive design, to Grid Systems.
Bootstrap is useful for all developers, for users who only have the barebones HTML of a system Bootstrap can make your design stylish and user friendly without requiring a designer...
It's lightweight and most of the features can be used simply by including the minified CSS, meaning you can drop Bootstrap into your projects just to use a few features without comprimising your load times.
Be careful though, you don't want to rely on Bootstrap for everything, all your websites could look the same!
These are very useful & easy to implement dropdown buttons.