Getting image icon

Studying webpages to learn html/css/javascript

Got confused when I thought that most images were linked to or loaded locally... It seems like on spotify their search button is using something I don't understand to load the magnifying glass.

.spoticon-search-32:before {
    content: "\f141";
    font-size: 32px;
}

If I edit content the picture of the search button goes away so I know its the content that is responsible for the picture. But where the hell is it loading it from? it's not a .png or .jpg extension either...

via Chebli Mohamed