About Bootstrap Grid system

Question

I\'m confused about this part of code in the source code of bootstrap 3.3.5

/*line 1585 - 1590*/
.container {
  padding-         


        

Answer 1

Bootstrap columns have 15px left and right padding so that their content is properly spaced out. However, this pushes the first and last column’s content 15px away from the parent. To compensate, the row has negative left and right 15px margins. This is why you should always place columns within rows.