The Summer Paralympic Games are the world's second-largest sporting event, after the Olympics. Since 1988, they have been held every four years in the same city that hosts the Olympic Games.

"The Paralympic Games represent the peak moment of each quadrennial sports cycle for Paralympic athletes and constituents of the Paralympic Movement," states the constitution of the International Paralympic Committee (IPC), the governing body for the Paralympics. "They form the ultimate goal to which national, regional and world championships and other competitions lead up to."

The IPC defines a Paralympian as a person who has "an impairment that leads to a permanent and verifiable Activity Limitation." Further, the impairment should "limit the athlete's ability to compete equitably in elite sport with athletes without impairment." Athletes who have only a temporary impairment, such as a broken arm, are ineligible to compete. Additionally, if an athlete claims to have an impairment when they do not - termed "misrepresentation" by the IPC - they can potentially be banned for life from competing in the Paralympics.

There are six different "categories" of impairments that differentiate Paralympians: amputee, cerebral palsy, visual impairment (such as blindness), spinal cord injuries, intellectual disability, and a category called "les autres" (French for 'the others'), which includes those who don't fit into the other groups - such as dwarfism or multiple sclerosis. Within each disability category, athletes are divided further by their level of impairment, from mild impairment to severe. Athletes typically only compete against others with a similar level of impairment.

Paralympians also don't have to be born with an impairment. One of the most inspiring stories at the Games is likely to be that of Martine Wright, who lost her legs in the 2005 al Qaeda-planned terrorist attacks in London. Wright will compete as part of Britain's sitting volleyball team.

Impressive feats

Yet simply because an athlete has a disability that may make it difficult to compete against athletes without disabilities doesn't mean they aren't capable of incredible feats. In fact, some of them do compete against athletes without impairments - in the Olympics, no less.

Take for example, South African runner Oscar Pistorius. Known as the "Blade Runner" because of his use of blade-shaped prosthetics he uses after both his legs were amputated at age 11, he competed in the 400 meters and the 4x400 relay at the 2012 London Olympics. Though he failed to medal, he advanced to the semifinals in the individual event and helped his relay team earn a season-best in the final of that event. Disabled or not, 45.07 seconds (Pistorius' personal record) is blazing-fast for anybody to run 400 meters.

Another South African Paralympian, swimmer Natalie du Toit, finished 16th in the women's 10km marathon swim at the 2008 Beijing Olympics. She finished less than 90 seconds behind winner Larisa Ilchenko of Russia, who was not impaired. Though she lost part of a leg after being hit by a car in 2001, du Toit swims without the aid of prosthesis.

Olympic likeness

The hope many have for the Paralympics is that athletes don't just succeed, but inspire others - just like the Olympics.

"We want to change public attitudes towards disability, celebrate the excellence of Paralympic sport and to enshrine from the very outset that the two Games are an integrated whole," said London Olympics and Paralympics organizing chief Sebastian Coe.

"There's a fantastic buzz in the air, waiting for it to kick off and people talking about it," IPC president Philip Craven told news agency AFP about attitudes leading up to the Paralympics.

The first Paralympics were organized by Sir Ludwig Guttmann, a German-born neurologist who in 1948 hosted sports competitions for injured British war veterans. With the aim of creating a sports competition for people with disabilities that would be equivalent to the Olympics, the Paralympics became international when a team of Dutch veterans decided to compete against the Brits in 1952. The first Paralympics open to more than just war veterans were held in Rome in 1960.

The Paralympics run from August 29 until September 9, taking place in many of the same venues as the London Olympics.