An Egyptian security guard screams at people as medics bring in a stretcher to carry the wounded after the attack which killed President Anwar Sadat, October 6, 1981, as he watched a military parade. (Photo by AP Photo)

Monsoon thunderstorm in Sierra Vista, Arizona. 9 Sept, 2011. (Photo by Steven Maguire)

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.

People travel in a taxi carrying sheep on a luggage carrier and in the car boot in Kandahar October 30, 2021. (Photo by Bulent Kilic/AFP Photo)

A man transports chicken on a motorscooter to the chicken market in Kathmandu, Nepal, 07 February 2023. Cases of bird flu, or avian influenza, infections have been confirmed in three places in the Kathmandu Valley, according to the Ministry of Agriculture and Livestock Development (MoALD), causing a drop in sales of chicken in the valley after the spread of the flu news. (Photo by Narendra Shrestha/EPA)

Spot-billed pelican interact on the banks of an artificial lake in Colombo on September 28, 2021. (Photo by Ishara S. Kodikara/AFP Photo)

Fashion models Darien Leigh and Valerie Drew play leap-frog on the beach. 2nd July 1956. (Photo by Harry Kerr). P.S. All pictures are presented in high resolution.

A woman dressed in an alien space suit carries an American flag and a sign that reads “Women's Revolution 1971” as she marches in a Women's Liberation demonstration on Fifth Avenue in New York, August 26, 1971. (Photo by Marty Lederhandler/AP Photo)