Min:
@media (min-width: @screen-sm-min) // >= 768px (small tablet)
@media (min-width: @screen-md-min) // >= 992px (medium laptop)
@media (min-width: @screen-lg-min) // >= 1200px (large desktop)
Max:
@media (max-width: @screen-xs-max) { // < 768px (xsmall phone)
@media (max-width: @screen-sm-max) { // < 992px (small tablet)
@media (max-width: @screen-md-max) { // < 1200px (medium laptop)