Bootstrap3 comes with a 12-column grid which is frequently used for building responsive websites.
You can use all 12 columns individually or you can group the columns together to make wider columns:
|col 1||col 2||col 3||col 4||col 5||col 6||col 7||col 8||col 9||col 10||col 11||col 12|
|col 4||col 4||col 4||col 4|
|col 6||col 6|
Bootstrap’s grid system is responsive, which means that the columns will re-arrange automatically depending on the screen size.
To be sure that the columns appear on a separate horizontal group, we must use rows.
Rows allows us to create horizontal groups of columns.
To use boorstrap grids, first we need to create a row (<div class=”row”>), and then add the desired number of columns in it.
Add up to 12 columns for each row.