If you’re familiar with programming languages, Sass maps are similar to arrays (in PHP or JavaScript) or dictionaries (in Python). If you’re not, think of them as lists that group similar items together.

A Sass map has keyword (key) and value pairs and is used to group similar variables - for example theme colours or breakpoints. They then get used with the map-get function - with the map as the first parameter and keyword:

$theme: (
  primary: #f00,
  secondary: #0f0,
  neutral: #f2f2f2
);

a {
 color: map-get($theme, primary);
}

div {
  background-color: map-get($theme, neutral);
  color: map-get($theme, secondary);
}

Sass maps are extremely useful for making your code more readable and consistent. Using a map, you can loop through your results, making your CSS less repetitive. For more on this checkout out the Sass @each loops snippet.

If you don’t want to have a key/value pair, Sass lists can be used for simple lists.