Chicago plays exactly like Stud, with one minor difference: out of the players who reach the showdown, the person with the highest spade (only hole-cards are eligible for this rule) wins half the pot. In a word, if you happen to have the As tucked into your pocket, bet away, as you’re certain one half of the pot will be yours.

Low Chicago is about the same as the High Chicago variant, with one difference: yes, you’ve guessed it, the spade in the pocket has to be the lowest. (2s is the nut here)

If the guy who shows down the best poker hand, also has the highest (or the lowest if it’s played with the low-spades rule) spade, he wins the entire pot.