Every second Tuesday of the month Microsoft releases security and critical patches for their products, this is referred to as patch Tuesday. On the fourth Tuesday of the month Microsoft releases non-critical and optimal updates for their products. The days are referred to as Patch Tuesday or Super Tuesday. (A reference to the day when the US. Presidential nomination race is decided.)
This month bunch of patches closes security holes for 64 known vulnerabilities and adds two extra security features. One is a module that validates executable code in office file formats, and the other is a root kit removal tool for the OS component WinLoad. The root kit removal tool is not aimed at a specific root kit, but scans all driver files for generic root kit fingerprints.
US CERT: http://www.us-cert.gov/cas/techalerts/TA11-102A.html
MS website: http://answers.microsoft.com/en-us/windows/forum/windows_other-windows_update/microsofts-patch-tuesday-vs-super-patch-tuesday/f2b4f0f0-f497-462d-96b9-e22c7df21873