In this Saturday, March 3, 2018, photo, a contestant gets ready to throw a hatchet at a wooden bull's-eye at the Kick Axe Throwing venue in the Brooklyn borough of New York. Kick Axe Throwing is the first bar in New York City to pick up on a nationwide trend of ax throwing, a growing sport that some enthusiasts hope will take off the way bowling did in the last century. (Photo by Mary Altaffer/AP Photo)

Members of the Moroccan Royal Armed Forces Rescue and Relief Unit take part in a biochemical simulation organized by the US Defense Threat Reduction Agency (DTRA) as part of the “African Lion” military exercise, in the port of Agadir, on June 15, 2021. (Photo by Fadel Senna/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.

A clothing shop displays its merchandise in the rebel-controlled city of Idlib, Syria November 7, 2015. (Photo by Ammar Abdullah/Reuters)

Indian police detain a Tibetan activist during a protest held to mark the 57th anniversary of the Tibetan uprising against Chinese rule, outside the Chinese embassy in New Delhi, India, March 10, 2016. (Photo by Cathal McNaughton/Reuters)

From footballs to live fish, delivery mopeds piled high with unwieldy, unlikely goods are one of the Vietnamese capital’s most distinctive sights. As the city plans to ban motorbikes altogether, photographer Jon Enoch captured the drivers at work. (Photo by Jon Enoch/The Guardian)

A pink elephant balloon, one of the entries in the Canadian Hot Air Balloon Championships, lands in a field in High River September 27, 2013. The event is a qualifier for the World Hot Air Balloon Championships in Sao Paulo in 2014. (Photo by Mike Sturk/Reuters)