Dividing the row into six parts by using class
.row class create a row and then under that row create the columns class named
.col-md-6 used to create the two columns in a row. Similarly
col-xs can also be used according to requirement.
Two different classes
.col-md-9 are used to divide the row in ratio of 3:9
.xsclass used for mobiles.
.smclass used for tablets.
.mdclass used for dekstops.
.lgclass used for large screens.
.hidden-lg classes is shown for responsive design.
Note:change the size of browser and try to analyse the use of classes.
.visible-lg are used here.Change the size of browser and try to analyze what these classes are doing.