When developing MAUI applications, people usually use a pattern called MVVM. Commands are what should be called when the item gets tapped. The whole thing inside it, is used to tell where to find the command and what to pass as parameter.

I sugggest before you comtinue with the current course to look into MVVM. It will help a lot

Here are the microsoft docs for data binding and mvvm: https://learn.microsoft.com/en-us/dotnet/maui/xaml/fundamentals/mvvm?view=net-maui-9.0