SASS-MQ is a third party mixin which allows us to more easily compose media queries. We give our project breakpoints easy to remember labels relating to viewport px size, which the SASS-MQ mixin then queries to match key to value.
Here's a few basic examples of how to use the SASS-MQ mixin. Many more can be found in its documentation here.
A function allowing you to add or edit breakpoints in
$mq-breakpoints, which are used by SASS-MQ).