An image of the popular video game “Angry Birds” is displayed on an iPod Touch on March 18, 2011 in San Anselmo, California. The “Angry Birds” mobile device video game developer Rovio is begnning the process of seeking an initial public offering (IPO). (Photo Illustration by Justin Sullivan/Getty Images)

The Empire State Building towers over the Manhattan skyline as tourists gather on the observation deck of Rockefeller Center on February 13, 2012 in New York City. The owner of the Empire State Building, Malkin Holdings, plans to raise up to $1 billion in an initial public offering on the 102 story Manhattan landmark. (Photo by John Moore/Getty Images)

Krastsvetmet, located beside the beautiful Yensei river in the metropolis of Krasnoyarsk, Russia, is a refinery of all types of precious metals on an industrial scale.

In this handout provided by Maritime New Zealand, MV Rena is seen in two pieces after overnight bad weather pounded the vessel, on January 8, 2012 in Tauranga, New Zealand. (Photo by Maritime New Zealand via Getty Images)

Astronaut Chris Hadfield Explains How to Wash your Hands in Space.

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.