Main players: InternetExplorer, FireFox, GoogleChrome, and NetscapeNavigator (which is now defunct, btw). Also see OperaBrowser and SaFari (wow that link was UgLy).

Basically, browsers fighting each other for market share. I wasn't on the Internet in the early days myself, but from what I can piece together (assuming we're talking about Windows):

• NetscapeNavigator came first of the major browsers.
• InternetExplorer won over NetscapeNavigator because it was the default browser shipped with Windows. So NetscapeNavigator is now basically dead (despite the 9.0 release in 2007, which nobody really uses except for the diehards).
• InternetExplorer development stalls for a few years. (IE6 was out for a long, long time.)
• FireFox grabs some of InternetExplorer's marketshare. Customization, extensions, all that jazz.
• Google decides to get in the business (as of this writing, 2009) with GoogleChrome. Which is fast and has minimal features.

Currently the browsers' advantages are: InternetExplorer is the Windows default browser, FireFox has lots and lots of extensions, and GoogleChrome is fast.

As for Opera and Safari, those are Mac browsers and, face it, people mostly just install FireFox. - NatalieBrown