Plug-ins are small computer bits of software that let you view a document, interact with an image, listen to music or watch a video.

If you did not have the right plug-in on your computer, you would not be able to listen to your favourite song or see animations and video on screen.

So, if you want to play a game that uses Shockwave and you don't have it on your computer you'll be prompted to install it.

Getting plug-ins

They are called plug-ins because they 'plug in' to your browser the first time you download them onto your computer, generally installing automatically.

When you go to a site that needs a plug-in your browser will automatically know and ask you whether you want to download the plug-in needed.

After that they start themselves whenever they are required - that is, whenever you visit a website designed to be viewed using a particular plug-in.

Typically, plug-ins add 'multimedia' functions which enable you to receive information in more powerful ways than the normal text and image - such as animation, sound or video.

Why plug-ins?

You may wonder why plug-ins are needed at all and why the main browser types don't automatically include every type of functionality as standard?

The answer is that this would simply not be practical. There are hundreds of plug-ins - with new ones created all the time - and a basic package could never include them all and be up-to-date.

Plus, it makes more sense to keep the basic browser as small a possible to make it easier to install and then leave it up to individual users to decide what extra functionality they require.