Windows Live is an internet product of Microsoft. Until 2005 its many services were under MSN. They moved them to Windows Live to show people that these services are made to work with Windows operating system. They used the term less after 2012.
The Windows Live family features many different services. The most famous service being Windows Live Hotmail. However, there are also many more free services provided by Windows Live which only requires one account to access. Google and Yahoo! compete against Windows Live with similarly diverse services.