Belgium's Lisa Ingenito competes in the Mixed Artistic Swimming duet technical final on August 15, 2022 during the LEN European Aquatics Championships in Rome. (Photo by Filippo Monteforte/AFP Photo)

Giving out with a yell, Elke Sommer is tossed on the trampoline as she trains for her movie role as an athlete, on the playing field of the University of California at Los Angeles, June 8, 1967. (Photo by AP Photo)

A photo taken on August 21, 2017 shows girls passing in front of a building with a display of the Soviet state founder Vladimir Lenin Order in Volgograd, Russia. Volgograd Arena will host several cames of the FIFA World Cup 2018. (Photo by Mladen Antonov/AFP Photo)

Cambridge policemen, known as “Bulldogs”, lined up for the University Bulldogs Chase, dressed in morning coats and top hats, 7th March 1936. (Photo by H. Allen/Topical Press Agency/Getty Images)

Dawlish Carnival 50th anniversary pram race featuring the famous Dawlish Black Swan in England on August 15, 2023. (Photo by nidpor/StockimoNews/Alamy Live News)

Azerbaijan's Mariya Stadnik (R) wrestles Mongolia's Otgonjargal Dolgorjav (L) in their women's freestyle 50kg wrestling quarter-final match at the Champ-de-Mars Arena during the Paris 2024 Olympic Games, in Paris on August 6, 2024. (Photo by Punit Paranjpe/AFP Photo)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

“Don't Leave Any Food On Your Plate”. The giraffes at Nairobi's Giraffe Manor are totally at home with humans. They will eat out of your hand, or even off your plate. Photo location: Giraffe Manor, Nairobi, Kenya. (Photo and caption by Gavin Werbeloff/National Geographic Photo Contest)