A plugin is a software component that makes it possible to add a feature to the program
Plugins give additional functionality to websites that is otherwise not available. This can vary from images, videos, sound, or animation. For example, when you want to watch a movie online, you may have encountered the requirement to download a plugin for the movie to play, such as RealPlayer or QuickTime.
Other popular plugins are Adobe Acrobat, Adobe Flash, Java, Shockwave, Silverlight.
Almost all website browsers (Chrome, Apple Safari, Mozilla, etc) have their official site where you can download the plugin (also known as extension and add-ons). It’s important that you download plugins from its official websites to safeguard your computer from harmful entities.