Universal Control is one of this year's key features. It will be available in iPadOS and macOS, among others, and allows you to control multiple Macs and iPads with the same mouse and keyboard. This way you can easily switch between devices. In the tenth beta of macOS Monterey, Apple is preparing for Universal Control, but it is still uncertain whether it will also be present when Monterey is finally released. The latest beta now states that the ‘beta’ is. If it is indeed present in the official version of Monterey, there may still be bugs in it. Apple did the same with iCloud Private Relay, which is already usable but also bears the beta label.
Universal Control was announced at WWDC 2021 in June this year. It wasn't in the iPadOS 15 betas, nor in the final release. As for macOS 12 Monterey, we are still waiting for an official release date. Apple may be announcing the Monterey release date at its October event on Monday, along with the unveiling of new Macs.
In macOS Monterey beta 10 it shows:
You can force enable Universal Control by going to System Preferences > screens to go. You will then see an option to remotely control your keyboard and mouse for others. You still can't use it, but the fact that it's now an option in System Preferences does give the impression that Apple is trying to get it finished before release. If you have two Macs running on Monterey, you can enable Universal Control by modifying internal system files, but you still have to be aware of bugs. Another feature we're really looking forward to is SharePlay. That too has been postponed.