India: A sweeper cleans the side of a road near a replica of the Eiffel Tower amid heavy fog in the early morning in the northern Indian city of Chandigarh January 18, 2010. (Photo by Ajay Verma/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 man walks in the street at the start of the new curfew to counter the COVID-19 in the center of Lyon, central France, Saturday, January 16, 2021. All of France will be under a stricter curfew starting Saturday at 6 p.m. for at least 15 days to fight the spread of the coronavirus. (Photo by Laurent Cipriani/AP Photo)

A Guinean kid poses for a photo in Conakry, Guinea on July 23, 2021. Children, most of whom start working after a certain age to support their families, have their hair braided in different ways and decorated with colorful beads on all special days, especially on holidays, despite these difficult conditions. (Photo by Ozkan Bilgin/Anadolu Agency via Getty Images)

A foreign passenger wearing a protective suit poses as they prepare for their flight at Manila's International Airport, Philippines, Monday, January 18, 2021. Coronavirus infections in the Philippines have surged past 500,000 in a new bleak milestone with the government facing criticisms for failing to immediately launch a vaccination program amid a global scramble for COVID-19 vaccines. (Photo by Aaron Favila/AP Photo)

Young couple in BDSM action on the leather sofa. (Photo by Alamy Stock Photo)

A fisherman with a close bond to cormorants uses the flock of birds to catch big fish in Li river in Guilin, China. The aquatic birds can be seen perching on a bamboo raft before swooping into the calm water to grasp hold of prey. (Photo by Julia Wimmerlin/Solnet News & Photo Agency)