Chrome Web Store - What is an extension?

Extensions let you add new features to your browser. For example, an email notifier extension can show an email alert in your browser toolbar so you don't have to log in to your email in a separate window to check if you have new messages. There are also extensions that work silently in the background, such as an extension that automatically formats and displays web pages in your preferred style.

Check out extensions by visiting https://chrome.google.com/webstore