A wedding couple poses for a photographer during a wedding photo shoot March 9, 2011 in Hanoi, Vietnam. Its is traditional for middle and upper class Vietnamese couples do a wedding fashion shoot posing for wedding portraits a few weeks before the wedding so that a wedding photo book is produced. (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.

Colorado Gov. John Hickenlooper shows off his socks--one with Democratic presidential candidate Bernie Sanders and the other with Republican candidate Donald Trump – before entering his former brewpub for a book signing event to mark the release of his autobiography Thursday, May 26, 2016, in Denver. Hickenlooper, who is term-limited, is doing book talk rounds this week, reviving speculation that he is positioning himself to join Hillary Clinton's presidential campaign ticket. (Photo by David Zalubowski/AP Photo)

A member of Extinction Rebellion Red Rebel Brigade protests against fracking gas outside Government Buildings in Dublin, Ireland on March 23, 2021. (Photo by Clodagh Kilcoyne/Reuters)

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

A destroyed tank sits by the side of a road leading to Abi Adi, in the Tigray region of northern Ethiopia, on Tuesday, May 11, 2021. The Tigray People’s Liberation Front was on top of a coalition that ruled Ethiopia for nearly three decades. That changed in 2018, when Prime Minister Abiy Ahmed rose to power as a reformist. Abiy alienated the TPLF with efforts to make peace with its archenemy, Eritrea, and rid the federal government of corruption. (Photo by Ben Curtis/AP Photo)

Cast member Yara Sophia of “RuPaul's Drag Race” visits the Empire State Building in New York City on June 24, 2021. (Photo by Stephen Lovekin/Rex Features/Shutterstock)

Revellers gather for the start of the Annual SantaCon Bar Crawl at Father Duffy Square, a section of Times Square, on December 14, 2019, in New York City. SantCon is an event where people make donations to charitable causes and dress up as a Christmas character and visit bars around the city. (Photo by Steven Ferdman/Getty Images)