Initialization List in C ++

I almost don't know C ++. Not an expert.

I am looking at existing code. I could not understand this following code.

typedef enum
{
    eEvent_MsgOk,            
    eEvent_InvalidMsgId,    
    eEvent_Failure,          
} eEventType;

class Rs232Event
{
public:
    Rs232Msg*     m_pMsg;    
    eEventType     m_eEvent;   

}
Rs232Event::Rs232Event(eEventType eEvent,Rs232Msg* pMsg)
 :  m_pMsg(pMsg), m_eEvent(eEvent)
{
    // not implemented on purpose
}

Here, using the initialization list, they initialize the values.

But the Rs232Msg class does not have one parameterized constructor.

But he has a constructor that takes 4 parameters.

I could not determine how his call was causing. But the code works without errors.