Queen vs. passed pawn

Hi , i am kind of new to chess so i might (probably) miss something so i am asking here. I am trieng to learn from lessons here and one of them is named Queen vs. passed pawn. There is queen bullying king and last pawn. But in some moments the pawn could take the queen , i dont understand why he did not. Can someone help me and explain me what did i missed ? Thanks a lot.

In this lesson the black pawn is moving down the board and is on the 2nd rank, trying to get to the 1st rank to make a queen. So all of whites manoeuvers with the queen are behind the pawn and the pawn cannot capture the queen. 

Thanks a lot i knew i missed something , i am totaly stupid didnt recognize the sides thinking he is on starting position therefore all movements would be before pawn.Thank you again sir.