A general view shows a column of steam emerging from Popocatepetl volcano, after an increase in volcanic activity with steam and ash eruptions have been registered recently, according to local media, as seen from San Andres Cholula municipality, in the state of Puebla, Mexico on February 1, 2023. (Photo by Henry Romero/Reuters)

Danusorn Sdisaithaworn, 10, poses for a portrait during an annual Poy Sang Long celebration, a traditional rite of passage for boys to be initiated as Buddhist novices, while he visits a relative's house outside Mae Hong Son, Thailand, April 4, 2018. (Photo by Jorge Silva/Reuters)

A fan waves a Brazilian flag before the arrival of the Olympic torch ahead of the Rio 2016 Olympic Games on August 2, 2016 in Sao Goncalo, Rio de Janeiro state, Brazil. The torch will arrive in the city of Rio tomorrow and the Games commence on August 5. (Photo by Mario Tama/Getty Images)

Boys play with a drainage culvert used for flood control in Las Pinas, Metro Manila February 28, 2016. (Photo by Erik De Castro/Reuters)

Archie, a Chinese Crested dog, sits with his tongue out before the start of the 20th Annual Ugliest Dog Competition at the Sonoma-Marin Fair June 20, 2008 in Petaluma, California. Owners of ugly dogs travel to Petaluma from all over the country to participate in the annual contest. (Photo by Justin Sullivan/Getty Images)

“It’s the end of the world, baby!” screams the title of the new 2012 calendar from Campari. Sensing the Mayan calendar’s apocalyptic spirit, Campari created a protagonist in supermodel Milla Jovovich to storm through the end of the world holding glasses and bottles of the red aperitif, all while dressed in impeccable couture. (Photo by Dimitri Daniloff/Campari)

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 September 16, 1983 file photo, actor and bodybuilder Arnold Schwarzenegger shows off his new U.S. citizenship papers as Maria Shriver, daughter of Sargent and Eunice Shriver, looks on at the Shrine Auditorium in Hollywood, Calif. (Photo by Wally Fong/AP Photo)