The Charleston is mahjong's version of trading up before the real game even starts: a set of structured passes (right, across, left, sometimes an optional "Courtesy" round after) where the whole table hands off tiles nobody wants, all at once, face-down. The name comes from the 1920s dance, and yes, the story is that someone thought the back-and-forth of passing tiles looked like the dance's footwork. Whether that's actually true is anyone's guess, but it stuck.
Three tiles a round, blind, no take-backs. That blindness is the whole game within the game. Pass too aggressively and you hand away something you needed twenty minutes later. Play it too safe and your hand never actually improves.
By the last round, most players already know which hands on the card are realistically in reach, and which ones they're quietly letting go. Prefer watching it happen over reading about it? There's a video walkthrough on our How to Play page.
Keep going with mahjong terms explained, or browse mats and tile sets in the shop.