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.

A man wearing a costume dives into a partly frozen lake in Shenyang, in China's northeastern Liaoning province on February 19, 2019. (Photo by AFP Photo/China Stringer Network)

A model presents a creation during the Vivienne Westwood catwalk show at London Fashion Week Women's A/W19 in London, Britain February 17, 2019. (Photo by Henry Nicholls/Reuters)

Models wear creations as part of the Moschino women's Fall-Winter 2019-2020 collection, that was presented in Milan, Italy, Thursday, February 21, 2019. (Photo by Antonio Calanni/AP Photo)

A woman counts her money as she sells flowers ahead of International Women's Day in central Kiev, Ukraine on March 7, 2019. (Photo by Gleb Garanich/Reuters)

A protester is taken away by police during an electoral campaign closing rally of Spain's far-right party VOX in Madrid, Spain on April 26, 2019. (Photo by Juan Medina/Reuters)

As an airliner prepares to land, a bird takes off at the Gravelly Point park near Reagan National Airport in Arlington, Va. on December 23, 2018. (Photo by Michael S. Williamson/The Washington Post)

Sophie Turner (L) attends HBO's Official 2019 Emmy After Party on September 22, 2019 in Los Angeles, California. (Photo by Jeff Kravitz/FilmMagic for HBO)