The World Wide Web is part of a larger global network known as the internet. The Internet consists of interconnected computer networks that are "linked by electronic, wireless and optical networking technologies" (Wikipedia). Web pages are document files containing content that is primarily text, but can contain images, videos, and audio files. They are linked through a technology called hypertext. Hypertext is really key to what makes the web surfable, and is used to link files together and create complex system of crossreferences.
Web servers are specialized computers that are always connected to the internet, and are configured to send web pages to browsers when requested. To operate a web server, you typically buy space from a web hosting company, but it is possible to host pages in other ways too.
People access the web through software called a web browser, you've probably used one already. Let's break down the steps in how the browser renders a page.