CDR: The call has ended. Local user initiated hangup.

Site A was connected to Site B and C. During the conference, Site B got disconnected by itself. I'm trying to find out reason why. In the CDR report of Site A, it says "The call has ended. Local user initiated hangup." 

Can someone please tell me the difference bw just "The call has ended" & "The call has ended. Local user initiated hangup." ?

I'll appreciated the help. 

Thanks