Custom Assembly and WCF Service configuration
Custom Assembly:
This is the layer that contains the custom assemblies with the implementation of the service contract, security policies and custom user validators.
WCF Service Configuration:
This is the XML that resides in the app/web.config file. It contains all the elements that are needed to configure a WCF service with its endpoint, binding and behavior configuration. Each one of these elements can also contain other elements to further define the communication details, security and behaviors for the service.
This diagram provides a simple visualization of the main elements and their association.