Participants ride horses, hold spears and wear historic armoured suits of the Middle Ages as they compete during the Saint George international knight tournament in Moscow, Russia, May 3, 2015. (Photo by Maxim Zmeyev/Reuters)

Heidi Klum direct a photoshoot for “Germany's Next Top Model” on set filming on Hollywood Boulevard, Los Angeles, USA on January 25, 2017. (Photo by Splash News and Picture)

Passengers wait at the departure hall of the Beijing Railway Station in central Beijing, China January 27, 2017 as China gears up for Lunar New Year, when hundreds of millions of people head home. (Photo by Damir Sagolj/Reuters)

“Igor Fyodorovich Stravinsky (17 June [O.S. 5 June] 1882 – 6 April 1971) was a Russian-born, naturalized French, later naturalized American composer, pianist, and conductor. He is widely acknowledged as one of the most important and influential composers of 20th century music. He was a quintessentially cosmopolitan Russian who was named by Time magazine as one of the 100 most influential people of the century. He became a naturalized French citizen in 1934 and a naturalized US citizen in 1945. In addition to the recognition he received for his compositions, he also achieved fame as a pianist and a conductor, often at the premieres of his works”. – Wikipedia

Photo: Composer Igor Stravinsky (right) and impresario Sergei Diaghilev in Seville during their Ballets Russes collaboration. (Photo by Hulton Archive/Getty Images). 1921

Mongolian herder, Khurelsukh, throws the carcass of a goat onto a heap as he struggles to deal with losing a quarter of his herd, on March 8, 2010 in Bayantsogt, Tuv province, Mongolia. (Photo by Paula Bronstein /Getty Images)

Artist Kong Ning wears a wedding dress made from respirators to highlight concerns about air quality and pollution in Beijing, China on December 1, 2015. (Photo by Luo Xiaoguang/Xinhua Press/Corbis)

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.

The 26th annual National Geographic Traveler Photo Contest is now accepting submissions. Official categories include: “Travel Portraits”, “Outdoor Scenes”, “Sense of Place” and “Spontaneous Moments”. The contest is accepting entries until June 30. Photo: “Forest lights”. Aurora Borealis over the forest of the Pyhae Luosto National Park, Finland. (Photo and caption by Nicholas Roemmelt/National Geographic Traveler Photo Contest)