Why are the css rules below in the font.css file?

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}
.sr-only-focusable:active,
.sr-only-focusable:focus {
  position: static;
  width: auto;
  height: auto;
  margin: 0;
  overflow: visible;
  clip: auto;
}

 

https://stackoverflow.com/questions/19758598/what-is-sr-only-in-bootstrap-3

9 minutes ago, Donnie95 said:

https://stackoverflow.com/questions/19758598/what-is-sr-only-in-bootstrap-3

What does this have to do with fonts?

They are a part of the Font Awesome framework.

https://github.com/FortAwesome/Font-Awesome/blob/4.x/css/font-awesome.css