In poker, the showdown is that moment when all the betting is completed and the moment of truth has come. Were you running a bluff or do you actually have that hand you represented? Did you chase and miss? Or maybe you chased and hit your card on the river...though for the sake of poker "etiquette" I hope not. Everything about the game leads to that moment. If you haven't won your hand by this time, it is all on the cards now.