Web development explained simply

Computers are used to share pictures, words, and movies (usually of cats) with other computers. The computers need to show the cats on boxes with tiny lights in them, but don’t know how. People like me tell the computer many words so that it knows how to change the tiny lights to look like a cat. We try to make the lights change very fast so that you don’t have to wait for your cats. Some days the lights are all wrong, and we have to tell the computer more words to make them look like cats again.

Brandon Jones, Google Chrome GPU Team, Quoted from mentalfloss