Microsoft added an Explore Pane to Bing search result page to provide a set of helpful tools in a consistent location that enable you to more easily navigate various categories of results relevant to your query, including web, video, image, news, local, shopping, and more. The Explore Pane is always present in the left hand pane with dynamic contents, and can contain three sets of tools: Quick Tabs, Related Searches and Search History.

More info: Search Blog