In fashion, a runway, catwalk or ramp, is a narrow, usually flat platform that runs into an auditorium or between sections of an outdoor seating area, used by models to demonstrate clothing and accessories during a fashion show. In fashion jargon, "what's on the catwalk" or similar phrasing can refer to whatever is new and popular in fashion. A runway could be as basic as a narrow space between rows of chairs or more elaborate setups with multiple catwalks. Most runway shows are held inside, for shelter against the weather, but there are times when runway shows are held outdoors. In the 2016 Paris Fashion Week, Chanel presented an elaborate setup by designing the hall as if it were an airport. The viewing guests sat as if they were awaiting their flights while the models walked around the airport approaching ticket counters.
The term catwalk was established for Runway in relation to narrow bridges used for construction. With the narrow platform structure, models walked with extreme caution and poise to avoid any falling or running into other models. Because of their graceful stature and careful walking, many referred to the runway as the catwalk, reminding them of the same grace and poise mimicking a cat's natural walk.
When a model scores an exclusive for a fashion label it means that they have been picked to walk for that particular designer only. This might launch their career, elevate their status in the fashion industry and 'guarantee' them spots on the world's best catwalks.
A collection of photos taken of models wearing a designer or manufacturers clothing that is sent out to fashion editors, buyers, clients, and special customers to show the designer's looks for the season. 
Sketches or illustrations were the first way that designers would present clientele with their line. This is before mannequins and live runway models were established within the industry. 
At the turn of the 19th century, exclusive fashion houses in Europe, distinctly Paris and London, were using formal presentations to showcase their latest line to clientele. One of the most notable designers of this concept, Charles Fredrick Worth, gained traction by displaying clothes on actual people instead of mannequins. As the popularity for these formal presentations expanded, it was in 1918 when fashion houses established fixed dates for Runway shows to occur. These occurrences took place twice annually, specifically for fashion houses to plan for and promote their lines to foreign buyers. These Runway shows were often held in department stores or hotels when they first began. European fashion houses would actively seek out buyers in the United States, specifically in larger cities, by hosting these runway shows. 
With the creation of runway shows, runway modeling took off with the establishment of agencies and professional modeling careers. Before professional agencies, fashion houses that runway shows often had their own in house models who would specifically be fitted and costumes for each show. By having in house models to present the clothes for runway, the fashion houses could ensure that the clothing was perfectly altered for presentation and bound to sell. However, as the demand for models grew, the modeling agency was established to represent runway models.