A web browser is a software application that retrieves and displays HTML documents and other resources on the World Wide Web. The first web browser, worldwideweb (later renamed Nexus), was created by Tim Berners-Lee in 1990, leading to a series of developments including Mosaic, Internet Explorer, Opera, Mozilla, Safari, and Chrome. Browsers operate by requesting resources from servers and presenting them to users, with the ability to enhance functionality through add-ons or extensions.