People take part in a Halloween street party at Lan Kwai Fong on October 31, 2016 in Hong Kong. Halloween, a contraction of All Hallows' Evening, falls on the day before All Saints' Day on November 1, a holiday when Christians remember their deceased loved ones. (Photo by Lam Yik Fei/Getty Images)

Same-sеx marriage supporters kiss outside the Legislative Yuan Friday, May 17, 2019, in Taipei, Taiwan after the legislature passed a law allowing same-sеx marriage in a first for Asia. The vote Friday allows same-sеx couples full legal marriage rights, including in areas such as taxes, insurance and child custody. (Photo by Chiang Ying-ying/AP Photo)

An anti-extradition bill protester throws a stone at a police station in Tseung Kwan O residential district, in Hong Kong, China, August 4, 2019. (Photo by Kim Kyung-Hoon/Reuters)

A police officer reacts to flames during a protest against Chile's government in Santiago, Chile on November 4, 2019. Unrest began in Chile last October 18 with protests against a rise in transport tickets and other austerity measures and descended into vandalism, looting, and clashes between demonstrators and police. Protesters are angry about low salaries and pensions, poor public healthcare and education, and a yawning gap between rich and poor. (Photo by Henry Romero/Reuters)

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.

“Grit and Glamour”, a retrospective of the late British photographer Elsbeth Juda, who fled Nazi occupation and came to England in 1933, is at the Jewish Museum, in London, until July 1, 2018. Here: Shelagh Wilson, Copacabana beach, Rio de Janeiro, 1951. (Photo by Elsbeth Juda Archive/Victoria and Albert Museum)

Tournament officials use golf carts to coax an alligator off of the 17th fairway and back into the water during the third round of the PGA Zurich Classic golf tournament at TPC Louisiana in Avondale, La., Saturday, April 24, 2021. (Photo by Gerald Herbert/AP Photo)

Runner-up; Hon Yen marine ecosystem. Phu Yen, Vietnam. Every year between May and August, the coral of this rich and diverse ecosystem becomes exposed at low tide. (Photo by Truong Hoai Vu/Royal Society of Biology Photography Competition)