Here are the data structures with brief descriptions:

CIOTHUB_CLIENT_COMMAND_REQUEST	This struct specifies parameters of an incoming command request
CIOTHUB_CLIENT_COMMAND_RESPONSE	This struct specifies parameters of an outgoing command response
CIOTHUB_CLIENT_CONFIG	This struct specifies IoT Hub client configuration
CIOTHUB_CLIENT_DEVICE_CONFIG	This struct specifies IoT Hub client device configuration
CIOTHUB_CLIENT_PROPERTY_PARSED	This struct represents a property from IoT Hub. It is generated by IoTHubClient_Deserialize_Properties() while deserializing a property payload
CIOTHUB_CLIENT_PROPERTY_REPORTED	This struct defines properties reported from the client. This corresponds to what DTDLv2 calls a "read-only property." This structure is filled out by the application and can be serialized into a payload for IoT Hub via `IoTHubClient_Properties_Serializer_CreateReported()`
CIOTHUB_CLIENT_PROPERTY_WRITABLE_RESPONSE	This struct represents the response to a writable property that the client will return. This structure is filled out by the application and can be serialized into a payload for IoT Hub via `IoTHubClient_Properties_Serializer_CreateWritableResponse()`
CIOTHUB_MESSAGE_DIAGNOSTIC_PROPERTY_DATA_HANDLE	Diagnostic related data