Nguyen Ngoc Anh, 36, who was an illegal logger turned forest protector poses at Phong Nha National Park, Quang Binh province, Vietnam on April 8, 2022. (Photo by Hoang Trung/Reuters)

People look at a funnel cloud formed near the beach in Barcelona, Spain, Monday, September 21, 2020. (Photo by Emilio Morenatti/AP Photo)

American rapper Belcalis Marlenis Almánzar, known professionally as Cardi B in the last decade of October 2022 says she's giving “you a*s, hair and heels”. (Photo by iamcardib/Instagram)

Illuminated installations light up the Heligan Night Garden on November 17, 2022, set amidst the atmospheric Lost Gardens in Cornwall. The Lost Gardens of Heligan have worked with The Lantern Company to illuminate the Gardens which is now open to the public. (Photo by South West News Service)

Photographer Gregg Segal travelled the world to document children and the food they eat in a week. Partly inspired by the increasing problems of childhood obesity, he tracked traditional regional diets as yet unaffected by globalisation, and ironically, found that the healthiest diets were often eaten by the least well off. (Photo by Gregg Segal/The Guardian)

Los Angeles Chargers wide receiver Keenan Allen runs onto the field before an NFL football game against the Pittsburgh Steelers, Sunday, November 21, 2021, in Inglewood, Calif. (Photo by Ashley Landis/AP 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.

Elephants spray tourists with water in celebration of the Songkran water festival in Thailand's Ayutthaya province, about 80 km (50 miles) north of Bangkok, April 9, 2014. (Photo by Rungroj Yongrit/EFE)