A model presents a creation by Chinese designer Chen Wen at China Fashion Week in Beijing, China March 29, 2017. (Photo by Jason Lee/Reuters)

Princess Charlene poses after the arrival of the Riviera Water Bike Challenge in support of the Princess Charlene of Monaco Foundation, in Nice, France, June 4, 2017. (Photo by Eric Gaillard/Reuters)

Mohamed Mostafa, 35, carries dyed yarns at a dye workshop in old Cairo, Egypt, March 17, 2016. Egypt's hard currency crisis and competition from modern factories in Asia and at home threaten one of the last dye workshops in Egypt. But one of its owners takes comfort in the trade's ancient resilience. Mohamed Mostafa boasts that the profession dates back 3,000 years, so it can survive anything. (Photo by Amr Abdallah Dalsh/Reuters)

A model is reflected in a mirror as she applies make up backstage during Kazakhstan Fashion Week in Almaty, Kazakhstan, April 19, 2016. (Photo by Shamil Zhumatov/Reuters)

An eight-year-old St Bernard with the longest canine tongue in the world, measuring 18.58cm (7.31in) in length, as recorded by the Guinness World Records: Amazing Animals, in South Dakota, USA. (Photo by Kevin Scott Ramos/GWR/PA Wire)

Sеxy brunet striptease dancer dancing lap dance in front of man. (Photo by Blue SkyImages/Getty Images)

Kamaz Russian driver Eduard Nikolaev, co- driver Evgeny Yakovlev and mechanic Vladimir Rybakov compete during the 2018 Dakar Rally' s Stage 13 between San Juan and Cordoba in Argentina, on January 19, 2018. (Photo by Franck Fife/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.