The Duet desktop and app software can extend an iPad as a second monitor. Using an iPad as a second display is helpful when traveling and extra screen realestate is important.
However, if you don’t have Catalina, use a Windows PC, or need more advanced features, Duet Air 2.0 may be the software you are looking for.
Download the Duet iPad app:
Download the Duet desktop app and install:
Start the Duet app on the iPad: