Getting her tongue pierced was “exciting and scary” says a teen who succumbed to pressure from her best friend in Austin, Texas, February 22, 2008. This image is featured in National Geographic's exhibition “Women of Vision: National Geographic Photographers on Assignment”, on view at the Palm Beach Photographic Centre, Jan. 22 - Mar. 22, 2015. (Photo by Kitra Cahana/National Geographic)

A publican serves a glass of stout to a donkey in the East End of London, 1960s. (Photo by Steve Lewis/Getty Images)

Kim Kardashian heads out in Miami wearing a see-through nude color top on September 17, 2016. (Photo by Splash News and Pictures)

Bathing suit models are shown listening to the radio on the beach, circa 1940's. (Photo by Bettmann Archive/Getty Images)

Revelers perform during the Myths and Legends parade in Medellin, Antioquia department, Colombia on December 8, 2021. (Photo by Joaquin Sarmiento/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.

Kashmiri vegetable vendors assemble at a floating market in the interiors of the Dal Lake in Srinagar April 17, 2012. (Photo by Danish Ismail/Reuters)

A person dressed up as Spider-Man sits next to the cabs as taxi drivers hold a protest against taxi-hailing apps such as Uber, Cabify and Didi at Angel de la Independencia monument, in Mexico City, Mexico, October 12, 2020. (Photo by Edgard Garrido/Reuters)