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.

Crowds watch surfers as the first big swell of the year arrives in Nazaré, Portugal on October 28, 2015. (Photo by Pedro Miranda/Demotix/Corbis)

A ghost glass frog in the Chocó rainforest, Ecuador in November 2020. The marbled swirling “hypnotising” eyes are thought to be helpful in attracting a mate. (Photo by David Weiller/WENN)

In this March 19, 2016 photo, Kay Pike transforms herself using body paint and latex into Superman while live streaming at her home in Calgary, Alberta. Pike refers to all her creations as her “little paint children”. She said it would be boring and lonely to do the painting without an audience. (Photo by Jeff McIntosh/The Canadian Press via AP Photo)

Divers perform underwater “Flying Apsaras” dance at Nanjing Underwater World on September 20, 2023 in Nanjing, Jiangsu Province of China. (Photo by Yang Bo/China News Service/VCG via Getty Images)

A woman dressed up as a zombie takes part in a zombie walk in the Gaslamp Quarter during the Comic Con International convention in San Diego, California July 13, 2012. (Photo by Mario Anzuoni/Reuters)

Servicewomen march during a rehearsal for the Independence Day military parade in central Kiev, Ukraine on August 20, 2018. (Photo by Gleb Garanich/Reuters)

British actress Elizabeth Hurley poses for photographers during a beachside event to promote her swimwear range in Cannes, France on May 23, 2006. (Photo by Michel Dufour/WireImage)