Earlier this year, Apple announced the Sidecar feature available with the installation of MacOS Catalina and iPadOS 13. Essentially, this allows your compatible Mac and iPad to work together using the iPad as an external touch monitor and more.
The “features” include: Extending or mirroring the desktop via wired or wireless connection, Multi-Touch gestures on the iPad, Touch Bar support even if your Mac does not have it, use of Apple Pencil for Mac apps that support drawing tablets and more.
Apple has published a Sidecar White Paper PDF available for viewing and download. You can also read more about set up and the system and hardware requirements here.
You can modify Sidecar functionality from the Mac System Preferences > Sidecar. These allow you to choose where to show the sidebar and Touch Bar on your iPad screen, and allows certain supported features when you double-tap on the side of your Apple Pencil (2nd generation).
A requirement that is sometimes overlooked is that both compatible devices to be signed in to iCloud with the same Apple ID. Also, if using the feature wirelessly, both devices need to have Bluetooth, Wi-Fi and Handoff turned on, be within 10 meters of each other and neither the iPad is sharing its cellular connection nor the Mac is sharing its Internet connection.
