It's what you're probably using to read this right now. A browser, or web browser (same thing), is the program people use as their interface to the World Wide Web. It interprets HTML code including text, images, hypertext links, java applets, etc. allowing you to view web sites and navigate from one to another. Currently, the two most popular browsers are Netscape Communicator and Microsoft Internet Explorer.
MoZilla http://mozilla.org
PhoeNix http://www.mozilla.org/projects/phoenix/
NetScape http://www.netscape.com/computing/download/
OpeRa http://www.opera.com/download/
LyNx http://gd.tuwien.ac.at/infosys/browsers/lynx/
LyNx for DOS / WinDows http://www.fdisk.com/doslynx/lynxport.htm
W3M http://prdownloads.sourceforge.net/w3m/
AppleSafari http://www.apple.com/safari/download/
MoSaic http://archive.ncsa.uiuc.edu/SDG/Software/mosaic-w/releaseinfo/download.html