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 villager pours pesticide from a bucket as Mount Sinabung spews ash at Kebayaken village in Karo district, Indonesia's North Sumatra province, on December 4, 2013. The country has ordered the evacuation of 15,000 residents near the active volcano. (Photo by Roni Bintang/Reuters)

Israelis take cover as a siren sounds a warning of incoming rockets fired from the Gaza Strip, in Ashkelon, southern Israel, Sunday, May 16, 2021. (Photo by Heidi Levine/AP Photo)

Bristol celebrates “wonderful diversity” at St Paul's carnival on Saturday, July 6, 2019. Thousands filled the streets for the city’s 51st procession highlighting the contribution of the Windrush generation. (Photo by Alex Turner/The Guardian)

American singer-songwriter, producer and former dancer Anastacia and teacher dancer Maykel Fonts perform during the “Dancing with the Stars” TV show in Rome, Italy on March 24, 2018. (Photo by PA Press Association)

An overview of “Closer”, an art projection by conceptual artist and photographer Wim Tellier, at the King Baudouin Stadium in Brussels on June 15, 2021. Tellier, a Belgian photographer and artist, is known for his installation projects using giant-size photographs. (Photo by James Arthur Gekiere/Belga/AFP Photo)

Meerkats are weighed and measured during the ZSL London Zoo 's annual weigh-in on August 22, 2012 in London, England. The height and mass of every animal in the zoo, of which there are over 16,000, needs to be recorded. The measurements are collated in the Zoological Information Management System, from which zoologists can use the data to compare information on thousands of endangered species. (Photo by Oli Scarff)