The update has the KB3124263 demarcation. Microsoft has not yet published the KB page for this release.
The release is another cumulative update for Windows 10 PC users. It is not expected to include any new features, but it will have some minor improvements and bug fixes.
Windows Insiders are currently on build 11082, which was released on December 16 and is part of the forthcoming Redstone line. Those users will not see any update, but may have patches available too.
Update: Here is the changelog from Microsoft about this patch
This security update for Windows 10 Version 1511 includes improvements in the functionality of Windows 10 Version 1511 and resolves the following vulnerabilities in Windows:
- 3124605 MS16-008: Security update for Windows kernel to address elevation of privilege: January 12, 2016
- 3124901 MS16-007: Security Update for Windows to address remote code execution: January 12, 2016
- 3124584 MS16-005: Security Update for Windows kernel-mode drivers to address remote code execution: January 12, 2016
- 3124275 MS16-001: Security update for Internet Explorer: January 12, 2016
- 3118753 Microsoft security advisory: Updates for ActiveX kill bits: January 12, 2016