Sometimes, you may create classes solely for the purpose of extending them and never actually use them inside your HTML.
Sass anticipated this and allows for a special type of selector called a placeholder, which behaves just like a class or id selector, but use the
% notation instead of
Placeholders prevent rules from being rendered to CSS on their own and only become active once they are extended anywhere an id or class could be extended.
would translate to
Placeholders are a nice way to consolidate rules that never actually get used on their own in the HTML.