The video tutorial explains how to place a button in the center of a grid layout by using the column span keyword argument. It demonstrates how to make a button span over two columns to achieve a centered appearance in the second row. The tutorial provides a practical example by running an application to show the button's centered position, offering a useful technique for widget placement in grid layouts.

What is the visual outcome of using the column span keyword argument in the application?

Describe the process of placing a widget over multiple columns.