[ATL] I wonder why declare it so ?

Hi! 
I'm ATL begginer 
I'm live in a Korea.

while I study about atl, but I wonder why redefine Template as new 
user-defined datatype using typedef.

that is following source code
---------------------------------------------
template <class ThreadModel>
class CComobjectRootEx: public CComobjectRootBase {
typedef ThreadModel _ThreadModel;    //<------------- this is wondeful? 

public:
  ULONG InternalAddRef() {
    return _ThreadModel::Increment(&m_dwRef);
  };
  ULONG InternalRelease(){
    return _ThreadModel::Decrement(&m_deRef);
  }
};

  
Thank you!
Have a happy day! 





-- 
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