OCPP is a protocol that affects, controls and monitors many areas of a charging station's operation.
If you want to integrate this library with your charging station implementation, you have to register a couple of callbacks and integrate event handlers. This is necessary for the library to interact with your charging station according to the requirements of OCPP.
Libocpp needs registered callbacks in order to execute control commands defined within OCPP (e.g ResetRequest or RemoteStartTransactionRequest)
The implementation must call event handlers of libocpp so that the library can track the state of the charging station and trigger OCPP messages accordingly (e.g. MeterValuesRequest , StatusNotificationRequest)
Your reference within libocpp to interact is a single instance to the class ocpp::v201::ChargePoint defined in v201/charge_point.hpp for OCPP 2.0.1.