Style-Display Grid
Bootstrap 3.2 has once again changed identification of some elements of the layout control, but the basic principles still apply. The basic framework is based on a 12 column grid system, which is then modified by one of the four width settings. The width of elements can be varied depending on the screen size, and some blocks can be enabled or disabled depending on the device screen width.
CSS.Bootstrap is the official documentation, with the grid system forming an element of that along with the 'responsive utilities' providing what is better describes as visability controls.
Extra small devices Phones | Small devices Tablets | Medium devices Desktops | Large devices Desktops |
<768px | ≥768px | ≥992px | ≥1200px |
-xs | -sm | -md | -lg |
Visability of blocks is controlled by the use of .visible-* and .hidden-* and a combination of these can be used to control which blocks appear on which width range. In addition to this, .col-*.1 to -12 determin how wide a blcok is in a particular layout. The grid system documentation provides some nice examples of how this can be used.