Google asked the above question in Times Square, New York and only less than 8% of the people know what a browser is.
Now they want to tell you what a browser actually is by create this Youtube video and a website: http://www.whatbrowser.org. In that site, if you click on "A few useful tweaks", they will detect your current browser and tell you some useful tweaks about your browser. Also, you will find you actually can use other browser on your computer by clicking on "Try a New Browser." My recommendation for browser in this order: Google Chrome, Firefox, Opera, Safari and Internet Explorer.
[via Goolge Blog - http://googleblog.blogspot.com/2009/10/what-is-browser.html]