A C4C app is an app created for Planon-as-a-Platform (PaaP), which uses the Calendar Processing API. A C4C app is setup according to a best practice approach that is based on the way C4C app for Microsoft Graph API is built. The C4C-App development guide provides more detail on this subject.

A C4C app provides the connection between Planon ProCenter and the third-party reservation management system.

Typically, a C4C app will have some sort of subscription on events occurring in a resource in the third-party reservation management system and Planon ProCenter will be notified when these events happen.