WWW is short for the World Wide Web — the system of linked pages you look at in a browser. You say the letters one by one, 'double-you double-you double-you', which is famously slower to say than the thing it stands for, and that is part of why people gave up on saying it. Its real home is the front of a web address, as in www.google.com, where it is a leftover from the days when a company's computers each had a name and the one serving web pages was called 'www'. Today most sites work perfectly well without it, and many hide it, so young people often have never typed it. Notice also that WWW is not the same thing as the internet, though people mix them up. The internet is the network of connected machines underneath; the web is one thing running on top of it, and email, video calls and games run on the internet too without being 'the web'. In everyday talk almost nobody says 'the World Wide Web' any more — they say 'the web' or just 'online'. The full phrase now sounds slightly old-fashioned, the way it might in a textbook from twenty years ago.