An officer wipes sweat off the face of a Chinese People's Liberation Army (PLA) honor guard soldier as they rehearse for a welcoming ceremony for New Zealand's Governor-General Sir Jerry Mateparae at the Great Hall of the People in Beijing, Tuesday, July 21, 2015. (Photo by Mark Schiefelbein/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.

In this June 1, 2016 photo, Maria Arias stands near her kitchen as she puts on earrings while getting ready for school in Caracas, Venezuela. So many students have fainted from hunger at Maria's school that administrators told parents to keep their children home until they could find more food. (Photo by Ariana Cubillos/AP Photo)

An Afghan policeman frisks a man while a burqa-cald woman sits in the trunk of a car on a roadside in Herat, Afghanistan, 05 July 2015. At least 18 police, two civilians and 30 rebels were killed in central Afghanistan during three days of fierce fighting, police said on 04 July. The clashes ended 04 July after security forces retook control of nine police checkpoints that had fallen to the rebels. (Photo by Jalil Rezayee/EPA)

A woman wearing a mask to help protect against the spread of coronavirus, tries to communicate with Efe, a cat living in Kugulu public garden, in Ankara, Turkey, Monday, November 30, 2020.Turkey's President Recep Tayyip Erdogan has announced Monday the most widespread lockdown so far amid a surge in COVID-19 infections, extending curfews to weeknights and full lockdowns over weekends. (Photo by Burhan Ozbilici/AP Photo)

A clash has broken out among the police and the protesters on March, 25, 2021 against Indian prime minister Narendra Modi’s upcoming visit in Motijheel, Dhaka, Bangladesh. (Photo by Harun-Or-Rashid/ZUMA Wire/Rex Features/Shutterstock)

A child is seen during celebrations of Reindeer Breeder Day, the main holiday of indigenous peoples of the Russian Extreme North, in the village of Nosok on Taymyr Peninsula in north-central Siberia, Krasnoyarsk Territory, Russia on April 17, 2021. (Photo by Alexander Ryumin/TASS)