Lava gushes from the southern side crater of Mt. Etna, Europe's largest active volcano, near Catania, southern Italy Sicily, early Tuesday, May 25, 2021. (Photo by Salvatore Allegra/AP Photo)

Vietnam's Khuat Phuong Anh (R) celebrates winning the women's 800m final during the 31st Southeast Asian Games (SEA Games) at My Dinh National Stadium in Hanoi on May 16, 2022. (Photo by Navesh Chitrakar/Reuters)

A fisherman waits to catch fish as he sits atop a stilt in the sea in Koggala, Sri Lanka on July 4, 2019. (Photo by Dinuka Liyanawatte/Reuters)

Joseph Ford is a 39-year-old photographer from Brighton, UK. He creates images seamlessly camouflaging people into backgrounds using knitwear made by Nina Dodd. It can take Dodd, 51, up to 40 hours to knit one item of clothing. This image of a man posing in knitwear, camouflaging into tiles of the steps and wall, is a personal favourite of Joseph’s. (Photo by Joseph Ford/South West News Service)

Migrant children play with leaves during Christmas Eve at a shelter, as they travel with their parents as part of a caravan with humanitarian visas to transit throughout the country, in Monterrey, Mexico on December 24, 2021. (Photo by Daniel Becerril/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.

A nurse helps an injured bomb victim sitting at the back of a pickup truck at the Asokoro General Hospital in Abuja, April 14, 2014. A morning rush-hour bomb killed at least 35 people at a Nigerian bus station near the capital on Monday, raising concerns about the spread of an Islamist insurgency after the first such attack on Abuja for two years. Suspicion fell on Boko Haram, though there was no immediate claim of responsibility from the Islamist group mainly active in the northeast. Five hours after the blast, officials had given no death toll. Reuters journalists counted at least 35 bodies. (Photo by Afolabi Sotunde/Reuters)

Christopher Tubbs embraces his wife Sarah after arriving home during the homecoming of the USS Enterprise at the Norfolk Naval Station July 15, 2011 in Norfolk, Virginia. In its 184 days away from Norfolk, the USS Enterprise cruised nearly 60,000 miles while supporting operations in Afghanistan and Iraq. (Photo by Win McNamee/Getty Images)