Visitors pose for a picture next to a mallard duck on the cobblestones of St Peter's Square with St Peter's Basilica in the background at The Vatican, on May 5, 2025. (Photo by Alberto Pizzoli/AFP Photo)

Mott Sreymom, 34, a rat handler with the humanitarian demining organization APOPO, carries an African giant pouched rat back from a landmine field in Siem Reap, Cambodia, Tuesday, June 10, 2025. (Photo by Anton L. Delgado/AP Photo)

People smoke marijuana in front of the Brandenburg Gate during the 'Smoke-In' event in Berlin, Germany, Monday, April 1, 2024. Starting 1 April, Germany has legalised cannabis for personal use. As per the new law, Adults aged 18 and over will be allowed to carry up to 25 grams of cannabis for their own consumption. (Photo by Ebrahim Noroozi/AP Photo)

A model is reflected in the mirror applying makeup during the Mr. and Mrs. Kibera leadership contest, on International Youth Day, in Nairobi, Kenya, Tuesday, August 12, 2025. (Photo by Brian Inganga/AP Photo)

A model poses at Checkpoint Charlie, a historic place in the German capital to promote the fashion magazine “Sous” on June 12, 2012. (Photo by Maurizio Gambarini)

Mongolian herder, Khurelsukh, throws the carcass of a goat onto a heap as he struggles to deal with losing a quarter of his herd, on March 8, 2010 in Bayantsogt, Tuv province, Mongolia. (Photo by Paula Bronstein /Getty Images)

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.

Artist Kong Ning wears a wedding dress made from respirators to highlight concerns about air quality and pollution in Beijing, China on December 1, 2015. (Photo by Luo Xiaoguang/Xinhua Press/Corbis)