White has just Promoted his e-file Pawn, which has been exchanged for another Queen, at e8 ... Black can only move his King, and advances it away from the coming danger, to c2.
Before White finalises the win, he moves his Rook out of potential danger, from Black's King, all the way up to a8 ... Black now has no hope - he could Resign and avoid the inevitable Checkmate, but chooses to see it out to the end, by moving his King to c3.
White begins his Checkmate strategy of shepherding Black's King to the very edge of the board - in this case, toward the a-file ... White, first, moves his Rook to c3, which Checks (+) Black's King; Black is now restricted and moves away to b2.
White sends his d-file, Promoted Queen, to c8, which again puts Black's King in Check (+) ... Black withdraws his King further away, to a2, his final move - soon to be with NO escape.
White marches another Queen all the way down to a4, which not only "Checks" Black's King herself, but seals the victory, with Checkmate (#) against White.
So, White Wins the game (1-0)
- e8Q ... Kc2
- Ra8 ... Kc3
- Rc8+ ... Kb2
- Qb6+ ... Ka2