MSN (or Microsoft Network) is an internet service provider created by Microsoft on August 24, 1995, coinciding with the release of Windows 95. The MSN moniker has since been extended to Microsoft's Hotmail webmail service and the MSN Messenger instant messaging client, as well as other Microsoft-branded websites.
With 9 million subscribers, MSN is the second largest ISP in the United States behind Time Warner's America Online service with 26.5 million.
Interestingly, recently the word "MSN" has come to be synonymous with "MSN Instant Messenger" in "internet slang"