How does Enterprise Mode help you stay up-to-date?
Many businesses are experiencing tension between today’s Web apps and services—which may require modern standards like HTML5 and CSS3—and older Web apps and services, designed for older versions of Internet Explorer. Legacy apps often represent a significant investment and have long, multi-year lifecycles, effectively making these customers dependent on an older version of Internet Explorer until they can upgrade these Web apps to modern Web standards.
Introduced in 2009, Internet Explorer 8 was the first browser available on Windows 7 and included innovative features like Compatibility View for older Web sites. Because it also ran on Windows XP, many customers and developers chose to standardize on Internet Explorer 8 to help ease the migration to Windows 7. According to Net Applications, Internet Explorer 8 still has more than 20% of the desktop browser market share; despite the fact that IE9, IE10, and IE11 have superseded IE8, many customers still rely on Internet Explorer 8 to run their business.
By providing better backward compatibility for Internet Explorer 8, Internet Explorer 11 with Enterprise Mode is intended to help break this dependency and provide the best of both worlds: A modern, up-to-date browser that helps customers extend their existing investments in older Web apps.
More info here