iOS 16.3.1 and iPadOS 16.3.1 are now available to download. The update can be downloaded from this moment and to do this you need to go to Settings > General > Software Update on your device.
Click Download and Install once the update appears. It features iCloud performance fixes, Siri, Find My, and Crash Detection improvements for iPhone 14 and iPhone 14 Pro.
The full iOS 16.3.1 notes are as follows:
iCloud options may not respond or display properly if apps use iCloud
Siri requests for Find My may not work
Improved Crash Detection for iPhone 14 and iPhone 14 Pro

Along with iOS 16.3.1 Apple also updated other platforms such as:
HomePod
iPadOS 16.3.1
tvOS 16.3.2
watchOS 9.3.1
macOS Ventura 13.2.1
The beta phase has already started for iOS 16.4 where Apple has promised some innovations such as Apple Music Classical but there is still nothing official.