An example of using Bootstrap's standard rows and columns for page layout in sections or blocks.
Using the simple class col (as done here) will work if columns contain very little, or very small graphics — but this layout will NOT be responsive for small screens — see Rows and columns (2). To create complex responsive layouts with Bootstrap styles, you need to learn about Bootstrap's grid system.
See Rows and columns (3) for an example that is responsive with more content in each column.