Silhouetted against the warm sunset skyline and the illuminated Tokyo Tower, visitors are reflected on the glass walls of a rooftop observation deck Thursday, January 21, 2021, in Tokyo. (Photo by Kiichiro Sato/AP Photo)

Yoga enthusiasts perform a yoga exercise in a wine yoga class inside “Van Gogh: The Immersive Experience”, a multi-sensorial exhibition featuring artworks of renowned artist Vincent van Gogh at a department store in Bangkok, Thailand, August 5, 2023. (Photo by Athit Perawongmetha/Reuters)

A model holds a 18,18 carat pink diamond called “Fortune Pink” that could fetch 30 million U.S. dollars during a preview at Christie’s before the auction sale in Geneva, Switzerland on November 2, 2022. (Photo by Denis Balibouse/Reuters)

A mermaid poses under water during a shoot with photographer Brett Stanley during MerMagic Con at the Freedom Aquatic Center in Manassas, Virginia on August 7, 2021. MerMagic Con is advertised as the largest Mermaid convention in the world. Some parts of the convention are based on modeling and looks like the Miss Mermaid USA Pageant. The Society of Fat Mermaids looks to bring together plus size people and promote the idea that anyone can become a mermaid. Becoming a mermaid is not cheap, most merfolk spend thousands of dollars on their tail and outfit. Most tails are custom made out of silicone and others are foam and fabric. (Photo by Joseph Prezioso/AFP Photo)

Primary school students attend an emergency evacuation drill on China's national day for disaster prevention and relief on May 12, 2022 in Hefei, Anhui Province of China. China's national day for disaster prevention and relief falls on May 12 every year. (Photo by Ge Qingzhao/VCG via Getty Images)

A poster of Russian President Vladimir Putin is used as target practice along a trench on the frontline with Russia-backed separatists near Zolote village, in the Lugansk region, on January 21, 2022. Ukraine's Foreign Minister Dmytro Kuleba on January 22, 2022, slammed Germany for its refusal to supply weapons to Kyiv, urging Berlin to stop “undermining unity“ and “encouraging Vladimir Putin” amid fears of a Russian invasion. (Photo by Anatolii Stepanov/AFP Photo)

Diver Sven, still in disguise, cleans the aquarium glass after a Santa Claus visit to the fish at Sea Life Berlin on December 6, 2021. (Photo by Christoph Soeder/dpa)

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.