_base.box-sizing.scss

Changes the default box-sizing to ‘border-box’ which means padding and borders appear on the ‘inside’ of the element, rather than being added to the outside.

The way this is set up, is for all elements to inherit the box sizing from the base HTML element, so if we need to set a specific element to have a different box-sizing declaration, it’s child elements will also inherit that box-sizing.