In Privacy Duo, you want to correctly guess how others will answer risqué questions.
On a turn, the active player reveals two question cards: an orange card with answers labeled A, B and C, and a blue card with answers labeled 1, 2, and 3. Questions are along the lines of these two: "What do you like the most in bed?" "What would you do for €500?" The active player determines how they would answer these questions, e.g., A3, then lays face down the answer card containing this letter-number combination. Each other player lays down a card matching what they think the active player will say, after which all the cards are revealed, and whoever guessed correctly scores a point. The first player to score 5 points wins.
The twist in Privacy Duo is that each player has only three answer cards: one showing A1/B2/C3, a second showing A2/B3/C1, and a third showing A3/B1/C2. Thus, you can answer the questions without revealing your exact answers, and others can correctly guess what you'd do without actually knowing what that is!