What is .baml file and what's the use of this file? Who creates this file?
A compiled XAML file.
A XAML file can be compiled into a .baml (Binary XAML) file, which may be inserted as a resource into a .NET Framework assembly. At run-time, the framework engine extracts the .baml file from assembly resources, parses it, and creates a corresponding WPF visual tree or workflow.