Checkmate

Every rule you have learned points at this moment. Chess is not won by grabbing the most pieces; it is won by checkmate: a check from which there is no way out.

Checkmate. The queen attacks the king and every square around him, and the white king guards her, so she cannot be taken.

You know the three ways out of check: move the king, block the line, capture the attacker. Checkmate is simply the position where all three fail at once. Here the king on h8 cannot move (g7, g8 and h7 are all covered), there is no line to block (the queen stands right next to him), and capturing her is illegal because the white king watches g7.

The moment checkmate appears, the game is over. Nobody plays the final capture; the rules stop everything right there. That is why the king has no point value: he is never traded, only trapped. Compare the position below, where the same kind of check is merely an inconvenience:

Check, but not checkmate: nothing shields the king, so he simply steps out. f7, g7 and h7 are all free.

One thing worth engraving early: material does not matter. You can be ahead a queen and two rooks; if your king is checkmated, you lose. Checkmate outranks everything.