Overview
An API is the access door for an external application to interact with the S/4HANA Cloud.

By default, the APIs are not accessible in your SAP S/4HANA Cloud tenant.
Before you can use an API, you need to activate it and eventually define one or more (SAP S/4HANA Cloud) users with the permission to use the API.
Retrieving the Communication Scenario

Before you can activate an API, you need to identify a related communication scenario. The communication scenario is a logical object that bundles a number of inbound and outbound communication design-time artifacts.
Every API can be bound to one or more communication scenarios. The information can be found in the SAP API Business Hub, within the API specific page.
On the other side, when searching for a specific communication scenario in the SAP API Business Hub, you can find the list of the APIs that relate to a specific communication scenario.