Recommended height and width for promoted links background images - Why additional CSS is required for .ms-tileview-tile-conent

Question

In the this link the author recommends this 3 lines of code below be added, but I do not understand why as similiar code is found in the CSS seen at the top of the page in the link.

Can someone tell me what is occuring with the 3 lines of code below? The code works great, but I want to understand it.

Add this to the bottom of the CSS before closing the style tag.

.ms-tileview-tile-content img {
    width:100px!important;
    height:100px!important;
} 

Answer 1

As @Patrick says, the code above is only for overriding SharePoints classes for setting the size of the background image in promoted links and is only necessary to use when you change the size of the links themselfs (by using more css as per the linked question)