Wolfram Alpha is an extension that provides knowledge on a wide variety of topics.
You can get Wolfram Alpha here
Once you install the extension an icon should appear that looks like this
When you click on it a popup will appear that looks like this:
The popup is another search bar that you can use to search through Wolfram Alpha to find help on a wide variety on topics.
The other way to search with Wolfram Alpha is to highlight the text of a page and right click it. When you right click there will be an option to search with Wolfram Alpha.