##Tables in Bootstrap
Bootstrap uses a responsive 12-column grid system, which makes it easy to put elements into rows and specify each element's relative width. Most of Bootstrap's classes can be applied to a div element.
Note that in this illustration, we use the col-md-* class. Here, md means "medium", and * is a number specifying how many columns wide the element should be. In this case, we're specifying how many columns wide an element should be on a medium-sized screen, such as a laptop.
In the Cat Photo App that we're building, we'll use col-xs-*, where * is the number of columns wide the element should be, and xs means "extra small", like an extra-small mobile phone screen.
The row class is applied to a div, and the buttons themselves can be wrapped within it.