Marine One with US President Joe Biden onboard takes off from the South Lawn of the White House in Washington, DC, on April 16, 2024. Biden is travelling to Scranton, Pennsylvania. (Photo by Drew Angerer/AFP 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.

Surfer Hannah Cornett attends The 2014 ESPYS at Nokia Theatre L.A. Live on July 16, 2014 in Los Angeles, California. (Photo by Jason Merritt/Getty Images)

Prostitutes working on 10th Ave in New York, USA on June 29, 1997. (Photo by Jon Naso/NY Daily News Archive via Getty Images)

Erica Bougard of the U.S. competes in the high jump event of the women's heptathlon during the 15th IAAF World Championships at the National Stadium in Beijing, China, August 22, 2015. (Photo by Fabrizio Bensch/Reuters)

President Calvin Coolidge rides in a car during his inaugural parade in Washington, D.C., U.S. in March 1925. (Photo by Reuters/Library of Congress)

A truck driver, butcher and firefighter are some of the subjects in the latest project by the photographer Chris Crisman. This series portrays women at work and focuses on occupations traditionally seen as male dominated. Here: Firefighter Mindy Gabriel, from Upper Arlington, Ohio. (Photo by Chris Crisman/The Guardian)

A person dressed up as Spider-Man sits next to the cabs as taxi drivers hold a protest against taxi-hailing apps such as Uber, Cabify and Didi at Angel de la Independencia monument, in Mexico City, Mexico, October 12, 2020. (Photo by Edgard Garrido/Reuters)