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)

Miss Puerto Rico Stephanie Del Valle (C) reacts after winning in the Grand Final of the Miss World 2016 pageant at the MGM National Harbor December 18, 2016 in Oxon Hill, Maryland. (Photo by Zach Gibson/AFP Photo)

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.

Birds are seen at Kizilirmak Bird Paradise in Turkey's Samsun on April 22, 2021. Kizilirmak Delta Bird Sanctuary, which is on the UNESCO World Heritage Tentative List and hosts 359 to 487 species of birds in Turkey, became more active with the arrival of spring. (Photo by Mehmet Kumcagiz/Anadolu Agency via Getty Images)

American singer and songwriter Leslie Grace arrives for the “In The Heights” opening night premiere at the United Palace Theatre in the Washington Heights neighborhood in Manhattan, New York, U.S., June 9, 2021. (Photo by Jeenah Moon/Reuters)

Pakistan fans during the first one day international match at the Sophia Gardens, Cardiff on Thursday, July 8, 2021. (Photo by Bradley Collyer/PA Images via Getty Images)

Martina Maggio, Alice D'Amato, Lara Mori, Asia D'Amato, and Vanessa Ferrari of Team Italy pose in front of the rings during Women's Qualification on day two of the Tokyo 2020 Olympic Games at Ariake Gymnastics Centre on July 25, 2021 in Tokyo, Japan. (Photo by Mike Blake/Reuters)

A priest comforts one of the relatives of the victims, before a mass in their memory, as Lebanon marks one-year anniversary of Beirut port explosion, at the port in Beirut, Lebanon on August 4, 2021. United in grief and anger, families of the victims and other Lebanese came out into the streets of Beirut on Wednesday to demand accountability as banks, businesses and government offices shuttered to mark one year since the horrific explosion. (Photo by Aziz Taher/Reuters)