Detailed step of Dijkstra's algorithm performance analysis
Since makequeue takes at most as long as $|V|$ insert operations, we get a total of $|V|$ deletemin and $|V | + |E|$ insert/decreasekey operations.
  First of of all, why one algorithm has TWO kinds of insert operations, if they are the same kind, then where can we learn more about what decreasekey actually does?


No, there is only one kind of insert operation. We got 


$|V|$ deletemin operations.
a total of at most $|V|+|E|$ operations, where each operation is either an insert operation or a decreasekey operation. We count these two kinds of operations together because it takes the same asymptotic time to do either one of them, $O(\log |V|)$.  More specifically. we have


|V| insert operations during makequeue.
at most |E| decreasekey operations as each edge may or may not lead to a decreasekey operation.