Button groups allow you to group a series of buttons together on a signle line. Encapsulate buttons in <div> </div> element with class btn-group.
In the example below I used Bootstrap Grids by encompassing the button group inside an overarching <div> </div> element with class (row) and by adding classes col-*-* and col-*-offset-* to the <div> </div> that has class btn-group specified.
Button toolbars allow you to combine sets of button groups for more complex components.
In the example below I used class btn-toolbar to create a toolbar of button groups. I did so by encapsulating the <div> </div> element containing the btn-group(s) with an overarching <div> </div> element with class (btn-toolbar).
Instead of applying button sizing classes to every button in a group, button sizing classes can be added to a group (btn-group-sm, btn-group-lg).
If you want dropdown menus mixed in with a series of buttons then you can place btn-group within another btn-group. You do that by adding a <div> </div> element with class btn-group.