What does & do in css

Question

I am looking at some legacy code and found something like below in the css file:

.user_modal {
  width: auto;
  height\" auto;
  &.modal,
  &.fade.in
  {         


        

Answer 1

It looks like Sass or LESS. It's user_modal with those other classes in it that are not children of it. The & is a reference to the element/class above it.