Close up of a couple, with the woman holding the man's knee, underneath a table. (Photo by Peter Dazeley/Getty Images)

Silhouette detail of Republican presidential candidate, former U.S. President Donald Trump as he attends the first day of the Republican National Convention at the Fiserv Forum on July 15, 2024 in Milwaukee, Wisconsin. Delegates, politicians, and the Republican faithful are in Milwaukee for the annual convention, concluding with former President Donald Trump accepting his party's presidential nomination. The RNC takes place from July 15-18. (Photo by Andrew Harnik/Getty Images)

Finding just the right spot above the clouds at Camp 1 on Ama Dablam, Danuru Sherpa uses his iPhone to catch up with friends and family. Even at 18,500 feet (5,654 meters), climbers here can check their email and other dispatches from the world below. (Photo by Aaron Huey/National Geographic)

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.

A participant in the Crazy Races extreme sports game competes in the cross-country obstacle race in Ufa, Russia on September 21, 2015. (Photo by TASS/Barcroft Media)

A woman offers prayers by a road as a rickshaw puller transports passengers in Kolkata October 28, 2014. (Photo by Rupak De Chowdhuri/Reuters)

A zebra walks through the recently flooded Safari Park located at Safari World November 2, 2011 in Bangkok, Thailand. (Photo by Paula Bronstein /Getty Images)

Sean Phillips flies through the air as he demonstrates the JetLev water propelled jet pack that is strapped to his back at the Yacht & Brokerage Show on February 17, 2012 in Miami Beach, Florida. (Photo by Joe Raedle/Getty Images)