What is the basic architecture of Xamarin.Forms project?

Xamarin.Forms can consists of four (this varies based on requirements) projects under one solution.

• .NET Standard, PCL or Shared Project
• iOS Project
• Android Project
• UWP Project

Here, .NET Standard, PCL or Shared Project contains all UI & Business logic inside it.

iOS, Android, UWP contains platform specific code containing Renderers or Dependency Services Implementations.