I notice some websites make giant collages of various images from icons to buttons. An example I can find is Youtube. Here's an example of Youtube's "collage". These sites only display a portion of this image instead of displaying multiple images.
To clarify, say a site has five icons each of 10x10px. Instead of displaying them individually, they'll make a 50x10px collage, load the one image and display five separate instances of the image, but each one only showing the portion that's needed. For example, image 1 might be 10x10px beginning at 0px width, another might be a 10x10px image beginning at 20px width, etc.
What's the benefit of this compared to loading each image individually? Since the browser is only loading one image, I imagine it loads it faster than multiple images. Is this true?