What is the iOS 16.3 about

From Apple's info:

This update introduces a new Unity wallpaper to honor Black history and culture in celebration of Black History Month, Security Keys for Apple ID, and includes other enhancements, bug fixes, and security updates for your iPhone.

This update includes the following enhancements and bug fixes:

• New Unity wallpaper honors Black history and culture in celebration of Black History Month
• Security Keys for Apple ID allow users to strengthen the security of their account by requiring a physical security key as part of the two factor authentication sign in process on new devices
• Support for HomePod (2nd generation)
• Emergency SOS calls now require holding the side button with the up or down volume button and then releasing in order to prevent inadvertent emergency calls
• Fixes an issue in Freeform where some drawing strokes created with Apple Pencil or your finger may not appear on shared boards
• Addresses an issue where the wallpaper may appear black on the Lock Screen
• Fixes an issue where horizontal lines may temporarily appear while waking up iPhone 14 Pro Max
• Fixes an issue where the Home Lock Screen widget does not accurately display Home app status
• Addresses an issue where Siri may not respond properly to music requests
• Resolves issues where Siri requests in CarPlay may not be understood correctly

See: About iOS 16 Updates - Apple Support

Hi, so Freeform actually launched with iOS 16.2 but what ever. So this update has many bug fixes and security updates. It also has a new wallpaper wich is the black unity. That’s it.