Browsers can do most things for you but there are times when a specialist piece of additional software is needed, for example, to listen to some audio or perhaps video. This is called a 'Plugin'.

You needn't rush out and download all plugins that exist. It is more likely to be a reactive measure. You will arrive at a site to be told that you cannot view something unless you have a relevant plugin., make your choice then and download the plugin if you wish.