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)

Women members of the national police take part in a parade during a graduation ceremony in Bogota, Colombia on November 7, 2019. (Photo by Juan Barreto/AFP Photo)

Canadian actress Nina Dobrev needs an umbrella whilst leaving her hotel in Paris, France on March 4, 2019. (Photo by Splash News and Pictures)

A soldier looks at a line during a ceremony to mark Martyrs' Day at the Tiananmen Square in Beijing, China, 30 September 2022. Martyr's Day is celebrated on the eve of National Day of the People's Republic of China to commemorate the people who sacrificed their lives in pursuit of national independence. (Photo by Mark R. Cristino/EPA/EFE)

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)

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.