Plug-ins are separate pieces of software that you install on your computer and that work in conjunction with your browser and extend its capabilities. They let you see animations, tune into audio and video broadcasts, or move around in virtual 3-D worlds.

Many plug-ins have a history as helper applications: separate and independent programs that can be automatically launched by your browser to do things that the browser isn't equipped to do by itself. The majority of programs that were originally helper applications have now been re-issued as plug-ins for easy and seamless use right within your browser. Unlike helper applications, plug-ins can't do anything by themselves, but they enable your browser to play animations or sounds, display graphs and maps, and do other complicated things that used to be handled by separate helper applications.

There are over 100 plug-ins currently in development and on the market. For now, most of them are free for the downloading.

How they work

When your browser starts, it checks your computer for installed plug-ins. When you move around the Web, your browser will come across various file extensions embedded in the pages you load (for example, .dcr is a Shockwave animation file, .mov is a Quicktime movie). While a page loads, your browser opens up the plug-in that can support that type of file extension.

All you do is fill out a form online, download the installation program, and run it on your computer. Almost every plug-in site includes simple installation instructions. Make sure you choose the right plug-in for your computer and operating system (e.g. Macintosh, Windows 3, or Windows 95/98). Some plug-ins require more memory (RAM) than others; some will only work with newer browser versions.