Another debugger question

What does this mean and how can I use it to track down a bug?

*void operator delete() - delete a block in the debug heap
*
*Purpose:
* Deletes any type of block.
*
*Entry:
* void *pUserData - pointer to a (user portion) of memory block
in the
* debug heap
*
*Return:
* <void>
*

*dbgnew.cpp - defines C++ scalar delete routine, debug version

void operator delete(
        void *pUserData
        )
{
        _CrtMemBlockHeader * pHead;

        RTCCALLBACK(_RTC_Free_hook, (pUserData, 0));

        if (pUserData == NULL)
            return;

        _mlock(_HEAP_LOCK); /* block other threads */
        __TRY

            /* get a pointer to memory block header */
            pHead = pHdr(pUserData);

             /* verify block type */
            _ASSERTE(_BLOCK_TYPE_IS_VALID(pHead->nBlockUse));

            _free_dbg( pUserData, pHead->nBlockUse );

        __FINALLY
            _munlock(_HEAP_LOCK); /* release other threads */
        __END_TRY_FINALLY

        return;
}

#endif /* _DEBUG */