The new version of the software can be downloaded from the "Software Update" section of System Preferences on all compatible Macs.
According to Apple's release notes, the new software treats a "firmware problem" that affects Macs with a T2 chip. Apple provided no further details so we do not know what the specific firmware problem may be, but we can get more information when the security notes become available.
The Supplementary Update MacBook Pro addresses a firmware Issue with 15-inch MacBook Pro computers with T2 Security Chip and is recommended for all users.
For detailed information on the security content of this update, visit: https://support.apple.com/kb/HT201222
Apple published macOS Mojave 10.14.5 update in May 13, AirPlay adds 2 support to share music, photos, videos and more from Mac to AirPlay 2-enabled smart TV from companies like Samsung, Vizio, LG and Sony.
Small Apple News + interface changes were included that allowed users to follow a magazine directly from the catalog view, and there were improvements in audio latency on 2018 machines.