About the OS X El Capitan v10.11.1 Update - Apple Support

Emphasis below is mine

"The OS X El Capitan 10.11.1 update improves the stability, compatibility, and security of your Mac, and is recommended for all users.
This update:

• Improves installer reliability when upgrading to OS X El Capitan. 
• Improves compatibility with Microsoft Office 2016. 
• Fixes an issue where outgoing server information may be missing from Mail. 
• Resolves an issue that prevented display of messages and mailboxes in Mail. 
• Resolves an issue that prevents certain Audio Unit plug-ins from functioning properly. 
• Improves VoiceOver reliability. 
• Adds over 150 new emoji characters with full Unicode 7.0 and 8.0 support. 
• Resolves an issue that caused JPEG images to appear as a gray or green box in Preview."

About the OS X El Capitan v10.11.1 Update - Apple Support