Bing (www.bing.com), codenamed Kumo is the name of Microsoft's new web search engine, designed to compete with the industry leaders Google and Yahoo!. Unveiled by Microsoft CEO Steve Ballmer on May 28, 2009 at the All Things D conference in San Diego. Bing is a replacement for Live Search, and it went fully online on June 1, 2009. Notable changes include the addition of related searches (called "Explorer pane" on the left side of search results), search suggestions as you type, and the ability to keep track of your search history.

Source: Wikipedia

You can add Bing search to Mozilla Firefox by installing the following add-on:
https://addons.mozilla.org/en-US/firefox/downloads/latest/4610/addon-4610-latest.xml