For computer users devoted to the World Wide Web, their browser — Netscape or Microsoft Explorer, for instance — may seem magical, a quick route through mysterious cyberspace to Web sites around the world. Or the browser may be an annoyance at times, clunky and slow, providing frustration instead of instant gratification. But few users have any idea how a browser works. Even though the user seems to be transported to distant home pages, the pages flow into the user’s computer. Here is a look at how it really works.