Children riding on donkeys queue to fill their jerrycans with water from a cistern at a make-shift camp for the internally displaced in Yemen's northern Hajjah province on July 12, 2021, amidst an extreme heat wave and severe water shortage. (Photo by Essa Ahmed/AFP Photo)

People take photos in a field of Yellow Desert Sunflowers as wildflowers begin to bloom in Anza-Borrego Desert State Park in California after a record-setting wet winter of rain, Anza-Borrego Desert State Park, California, U.S. March 20, 2024. (Photo by David Swanson/Reuters)

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.

Somali couple Mohamed Noor (L) and Huda Omar pose for a photograph at their makeshift home during their wedding ceremony in Mogadishu's Rajo camp, Somalia August 17, 2016. Having met two years ago, the pair have just married at Rajo camp, where some 400 families live. Most, like Noor's parents, came here in the early 1990s to flee famine. (Photo by Feisal Omar/Reuters)

Fisherwomen laying barrels with salt in preparation for herring curing, 1937. (Photo by Topical Press Agency)

These Northern Lights “rainbows” have turned the sky greener than the Earth below. Vitaly Istomin, 26, spent several nights in freezing conditions under the stars in northern Russia’s Khibiny Mountains to capture the aurora’s “rainbows”. (Photo by Vitaly Istomin/Caters News Agency)

Aerial photo taken on March 4, 2017 shows cole flower fields in Luoping County, southwest China's Yunnan Province. (Photo by Xinhua/Barcroft Images)