[Isura]

MilkMan,

Showdown value simply means how strong/valuable your hand would be if it was forced to showdown against villain's hand. Say for example you were semibluffing the flop and turn with a flush draw; If you don't have a pair, A5s has greater showdown value than 87s. As a consequence, the 87s would be a better hand to bluff the river with, incase you can get villain to fold a small pair or ace high. But if your 87s pairs on the river, it may be worth it to just check since your hand now has some showdown value.