According to Apple’s release notes, the macOS update improves the security of the operating system. The update can be downloaded for free on all eligible Macs using the Software Update section of System Preferences.
iOS 14.8 and iPadOS 14.8, per Apple’s release notes, provide important security updates. The upgrades are available on all eligible iPhones and iPads over-the-air in the Settings app. To access the updates, go to Settings —> General —> Software Update on your iPhone or iPad.
watchOS 7.6.2 is also a security update. It can be downloaded through the dedicated Apple Watch app on the iPhone by going to General —> Software Update. To install the new software, the Apple Watch needs to have at least 50% battery, needs to be placed on a charger, and it needs to be in range of the iPhone