Bootstrap - Grid
Bootstrap grid system provides the quick and convenient way to create responsive website layouts.
Predefined grid classes:
“.col-*” classes to create grid columns for extra small devices mobile phones in portrait mode.
“.col-sm-*” classes to create grid columns for small screen devices like mobile phone in landscape mode.
“.col-md-*” classes for medium screen devices like tablets.
“.col-lg-*” classes for large devices like desktops, and the .col-xl-* classes for extra large desktop screens.
To read all details about bootstrap grid go to the link: