A young Afghan vendor waits for customers to buy sheep's heads at a roadside stall at the busy market in Kabul on November 29, 2015. (Photo by Wakil Kohsar/AFP Photo)

This 2014 series Shanghai Tian Wa saw Chinese photographer Liu Tao train his lens on two distinct districts in Shanghai. Here: “Shanghai Tian Wai №26, 2014”. (Photo by Liu Tao/The Guardian)

In this March 14, 2015 photo, tourists take pictures from a viewing area at Iguazu Falls in Brazil. From walkways and bridges, viewers can count 270 water falls almost 100 meters (330 feet) high. (Photo by Jorge Saenz/AP Photo)

A woman enjoys her last alcoholic drink on December 4, 2020 in Cardiff, Wales. Following a firebreak period that ran from October 23 to November 9 the Welsh Government have introduced new rules which will prevent pubs, restaurants and cafes from selling alcohol at any time from 6pm on Friday. The rules will be reviewed on December 17. (Photo by Wales News Service)

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.

Bikini Contest in Daytona Beach, Florida, USA. (Photo by Evan Hurd/Sygma/Sygma via Getty Images)

Alexandr Kudlay, 33, and Viktoria Pustovitova, 28, have breakfast in their apartment in Kharkiv, Ukraine on March 5, 2021. Tired of occasional break-ups, this Ukrainian couple found an unusual solution to stay inseparable. On St. Valentine's Day, they decided to handcuff their hands together for three months and began documenting their experience on social media. (Photo by Gleb Garanich/Reuters)

“These eerie formations in the sky may look like alien ships. But as the Daily Mail points out, they’re actually a natural occurrence called lenticular clouds”. – Claudine Zap. Photo: Lenticular clouds hover of the mountains of the Kamchatka Peninsula in Russia. (Photos by Denis Budkov/Caters News)