What is the difference between modules and services?

link source : www.pradoframework.com
Briefly, when a request comes in, the request passes through a service (usually TPageService), which handles request fulfillment via mmodules (usually THttp* and TPage).

Modules implement the IModule interface. Modules are "behind the scenes" libraries for the application. Among other roles, modules provide the "model" component of the MVC pattern (if MVC is the design pattern in use).

Services implement the IService interface. Services are bridges between the application and the user. Whenever a user sends a request to the PRADO application, it first goes through a service. Most applications rely exclusively on TPageService and don't implement others.