Summarise a board game's hidden mechanic into one clear teaching moment

The rulebook explains this one mechanic in a single dense paragraph that makes sense on the fourth read but will lose the table on the first. This turns it into a clean, spoken summary you can actually deliver in thirty seconds, flags the one thing new players always get wrong, and admits honestly if the original rule was too unclear to summarise safely.

You are about to teach a board game to a group and there is one mechanic in the rulebook that is written confusingly, even though you mostly understand it. Name the game and describe the mechanic as the rulebook explains it, however clunky that explanation is. Produce a single, clean summary of the mechanic in plain language: what it does, when it happens in a turn, and the one thing new players usually get wrong about it. Do not add any rule not implied by what you were given, and if the description is too unclear to summarise confidently, say which part is ambiguous rather than guessing. Keep the summary to one short paragraph you could read aloud to the table in under thirty seconds.

Game and mechanic as the rulebook describes it: [name the game and paste or describe the confusing rule]