At the moment of creating a new project, only shared project and standard .NET come out.
Before I could only choose shared project and PCL project.
.NET Standard has replaced PCL. .NET Standard 2.0 now offers a larger API surface then before.
See: https://channel9.msdn.com/Shows/XamarinShow/Episode-37-NET-Standard-Libraries-with-Immo-Landwerth and https://channel9.msdn.com/Shows/XamarinShow/Snack-Pack-25-New-NET-Standard-Mobile-App-Templates-in-Visual-Studio-2017