A registry object is an application registry. The existence of a registry implementation detail of pyramid. It is used by the framework itself to perform mappings of URLs to view callables, as well as servicing other various duties. Despite being an implementation detail of the framework, it has a number of attributes that may be useful within application code.
For information about the purpose and usage of the application registry, see Using the Zope Component Architecture in Pyramid.
The application registry is usually accessed as request.registry in application code.