Saturn's moon, Tethys, used to be a utopia. However, citizens stopped having children, and soon the population dwindled. The head of Tethys received permission from Earth to transport some earthlings to Tethys to ensure the population's survival. However, the best that earth had to offer were for a different purpose. The smartest, the fastest, the strongest, the best at a certain subject were taken for the games. The games are a holovision show that is used as entertainment on Tethys. The best that earth had to offer competes for a prize. What prize, you say? Royalty. The winner will be allowed to stay in the royal palace for a year, living like a king/queen, and have mountains of riches bestowed upon them. Of course, the contestants were taken against their will, which will only make this year's games more.. interesting.
The contestants are divided into groups of two. Whenever an episode airs, two teams will go head to head to try and win a specific challenge. Those challenges can be anything, from collecting as many apples as you can to solving a difficult riddle. When teams aren't doing challenges, they are allowed to live like average citizens, but all are roomed in a special building.
TL;DR: Teams of earthlings compete to win riches.