How does Bootstrap switch from one class to the next?

Question

I am trying to understand Bootstrap 3\'s responsiveness. I understand in css if you have 2 classes on an element, then the 2nd class will override

Answer 1

It is indeed the CSS that switches between these classes depending on the size of the screen using CSS @media queries (no javascript).

The col-lg-11 does not "override" the others. The col-md-6 is applied on medium width screens, and the col-sm-1 is applied on small width screens, so in this way the other classes override the col-lg-11.