This is a Channel 4 reality show. The first series of seven episodes was shown in 2013. The second series of four episodes was shown in 2016, with different presenters.
People, two at a time, enter the studio. After a brief conversation with the presenters, they enter a large, opaque, soundproof box which is in front of the presenters and the studio audience. After they have sex in the box, they come out of it and talk to the presenters about what they did in there.
Most of the conversations between the participants and the presenters aren't very interesting or informative. Most don't say much about why they chose each other or tell us how they or the audience can improve their sex lives. If they're not willing to give details, why choose to go on such a show on national television?
It's pointless for the participants to have sex in the studio's box, because no-one can see or hear inside the box. They're all fully clothed for the whole time that they're out of the box. They might as well have had sex at home or in their hotel, prior to going to the studio.
An American version was broadcast in 2015. Only five of its nine episodes were shown before it was axed.