In VC CDC HDC and pDC are distinguished connected and converted

CDC encapsulates the relevant operations of hDC. For example, an TextOut function of CDC hides its error detection, which can be completely simplified to the extent of CDC:TextOut(int x, int y, const CString& str)
{
    TextOut( m_hDC, x, y, (LPCTSTR)str, str.GetLength() );
}

m_hDC is the member variable of CDC HDC m_hDC;
CDC has an operator HDC() const {return m_hDC; }    
You can think of it as an HDC using

3.this is the pointer to the output target window of dc, through which the window handle can be obtained.    

    CPaintDC           dc     CClientDC             dc, GetDC,             ReleaseDC ReleaseDC  
    CWindowDC                       windows             any dc,     is equivalent to CreateDC,           DeleteDC

iv. Distinction and connection

HDC is a handle; CDC is a class related to Windows     devices encapsulated by MFC. CClientDC is a derived class of CDC that produces
objects corresponding to Windows client areas HDC is a data type of WINDOWS and is a device description handle.
CDC is a class in MFC that encapsulates almost all HDC operations.    
It can also be said that the variable defined by HDC points to a block of memory, which is used to describe the contents of a device, so it can also be said that     thinks that HDC defines a pointer; The CDC class defines an object,    , which has a device description table defined by HDC, and also contains functions for operations related to HDC.    
This is the same difference between HPEN and CPen, and POINT and CPoint.