[ServiceNow] What is the difference between service catalog and service portal?

Service Portal framework that allows administrators to build a mobile-friendly self service experience for users. 

It interacts with parts of the ServiceNow platform, so users can access specific platform features using Service Portal.

Service Catalog application, create service catalogs that provide your customers with self-service opportunities. 

Portals can be customised so that customers can request catalog items such as service and product offerings.