The rest of the sentence is "and you can add more features just for Mac". It implies you have an iPad app already. Even the part you quoted is about sharing code with an iPad app. And the rest of the page is all about porting.
"There’s never been a better time to turn your iPad app into a powerful Mac app."
"Bring your iPad app to Mac"
"Your iPad app can be made into an excellent Mac app. Bring your iPad app to life on Mac using the latest version of Xcode. Begin by selecting the “Mac” checkbox in the project settings of your existing iPad app to create a native Mac app that you can enhance further."
"Learn how to build a native Mac app from the same codebase as your iPad app."
While you are in the process of pasting it, the guys at ATP Podcast might also appreciate it.
> Native Mac apps built with Mac Catalyst can share code with your iPad apps
https://developer.apple.com/mac-catalyst/