Control directives give you a way to add conditional logic to your Sass code. They allow you to branch your code in different directions based on different conditions and they allow you to loop through code until certain conditions are true or they stop being true.
One of the ways CSS can be limiting is the lack of conditional logic and loops. You’re limited in your ability to set a style if one condition is true or while another remains true. There are media queries which offer some conditional logic, but odds are you’ve wished you could test against more conditions than media queries allow.