Lists are a series of values stored together as a data structure. On their own they’re not any more useful than regular Sass variables, however they become more useful when using the built-in functions Sass provides for working with them.
If you want to set a font-stack as a variable in Sass you could do something like $fonts: Helvetica, Arial, sans-serif in a single variable. Later you could assign the font stack with font-family: $fonts; However what if you only wanted to assign one of the fonts and not the whole stack? Sass lists might be your answer.
One of my favorite aspects of Sass is how easy the functions make it to work with colors. When I’ve studied color as a designer I learned color in HSL. When I’ve worked with color in CSS, it’s been either hexadecimal or rgb(a) values. The color functions in Sass helped me to bridge the gap between the different notations.
It’s been a few years since I started working with Sass and while there are a lot of reasons why I continue to use it, the built-in color functions are easily among my favorite features of the language. You can use them to mix two colors or lighten or darken another color. You can even use them to build complex color schemes from a single color.
Much of what you write in CSS is a string of some kind. Whether you’re setting a font-family as “lucida grande” or declaring a class as the selector .masthead, you’re working with strings. Despite how often strings are used in CSS, the language offers no way to manipulate them. Fortunately Sass does.