A "Search on GitHub" item is available when you right-click some selected text you may want to query on GitHub. A new tab opens up with the GitHub search results of the highlighted text as if you would have launched the query from the original site.
Furthermore you do not necessary need to leave your current working page and/or do some extra "clicks, copy & paste or typing" usually required for such request and thus can remain focus on your workflow and the management of your very volatile short-term memory.
