Two chimpanzees share a piece of watermelon at Taronga Zoo on December 23, 2010 in Sydney, Australia. (Photo by Rick Stevens/Taronga Zoo via Getty Images)

South Korean football fans react during a public screening in Seoul of the South Korea vs Russia football match at the 2014 World Cup in Brazil, early on June 18, 2014. (Photo by Ed Jones/AFP Photo)

Locks hang on a fence along the Cliff Walk in Newport, Rhode Island July 14, 2015. They say the whole world loves a lover, but in Newport, Rhode Island, at least, not everyone is fond of the so-called “love locks” that sweethearts are leaving along the resort city's famed seaside Cliff Walk. Hundreds of the padlocks left behind by tourists as romantic tokens now cover sections of a chain-link fence along the route. Each is meant to represent the bond lovers shared during their visit. By custom, the key is thrown away. (Photo by Brian Snyder/Reuters)

Lindsay Mann (L) and Anabella Mowbray kiss as they take photos of themselves laying in the confetti on 7th Avenue in Times Square on New Year's Eve in New York January 1, 2015. (Photo by Carlo Allegri/Reuters)

A man sits on the window of a burning building before falling from it, in central Lahore May 9, 2013. Fire erupted on the seventh floor of the LDA plaza in Lahore and quickly spread to higher floors leaving many people trapped inside the building. At least three people fell from the high floors trying to avoid fire that engulfed the building, local media reports. (Photo by Damir Sagolj/Reuters)

A model falls over on the runway during the SECCRY Hu Sheguang Collection 2014 Show during Mercedes-Benz China Fashion Week, March 30, 2014, in Beijing. (Photo by Lintao Zhang/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.