I was checking the polish train website and they have in their night offers: "sleeper 1 person", "sleeper 2 persons" and "sleeper touristic".
What does a "sleeper touristic" mean?
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While I never used one, I believe those are three-bed sleepers, like the one on this picture:
Source: Ivor Morgan on Seat61.com
Traditionally, they could be booked with 2nd class tickets unlike other sleepers, which might explain the different name (rules are more complicated now). See also Advice for travel by European overnight train in a sleeper or couchette on seat61.com and Seat types on European Trains on Eurail.com.