And External Programs Browsers have a limited range of abilities. Plug-ins and external programs provide ways to expand that range. Plug-ins generally will display within the browser display window.
External programs are just that, programs external to the browser.
When the browser is not able to deal with a file it receives, it passes it to an available application that is capable of dealing with the file. That application then starts, loads the file, and runs. In Netscape browsers, you can set which application each file type is sent to in Preferences. With Internet Explorer, the settings are made on a Windows control panel.