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.

Anja Rubik poses as she arrives for the screening of the film “Dolor Y Gloria (Pain and Glory)” at the 72nd edition of the Cannes Film Festival in Cannes, southern France, on May 17, 2019. (Photo by Stephane Mahe/Reuters)

Model Bella Hadid poses for photographers at the photo call for the film “Pain and Glory” at the 72nd international film festival, Cannes, southern France, Friday, May 17, 2019. (Photo by Arthur Mola/Invision/AP Photo)

A recruitment drive during the First World War at Trafalgar Square, London. (Photo by Central Press/Getty Images)

Looking towards the Times Building on Times Square, the Paramount Building is on the right, and Seventh Avenue on the left crossing Broadway. (Photo by General Photographic Agency/Getty Images). Circa 1930

The Lumix GX1 single lens reflex (SLR) camera with 14-42 mm powerzoom lens is displayed at the Panasonic booth at the 2012 International Consumer Electronics Show at the Las Vegas Convention Center January 10, 2012 in Las Vegas, Nevada. The new camera comes with an external viewfinder and flash and an ISO up to 12,800. The camera as shown sells for USD 949; the camera body alone is USD 799. (Photo by Ethan Miller/Getty Images)

A Russian trenchmortar crew run to take up a new firing position in the Stalingrad area during the Great Patriotic War. (Photo by Keystone/Getty Images). October 1942