Well Christian Dior launched a ready-to-wear line in New York in 1948 and the House of Dior includes many different lines. The reputation of the house was built on couture. In fact, at one point in the mid 50's it was said that the House of Dior was responsible for half of the couture sales in Paris.
The couture designs established the looks for each season, and the look trickled down into mainstream fashions through department stores and through private clients who were instrumental in setting fashions. The couture designs established fashions that trickled down into all levels of fashion. Private people bought couture pieces. Department stores bought pieces to copy, and there were licensed copies that were sold.
After the glory years of Dior couture in the 1950s, the business dwindled somewhat in later decades. Later designers, in particular John Galliano, really brought excitement back to the couture with over-the-top theatrical presentations. Some of his designs, obviously, were suitable only for the runway they were so theatrical and so over-the-top. Many of the designs are found in a modified form for gala evenings and runway creations. So the couture is really an important laboratory for designers where they work out their most extravagant concepts, and that's especially true at the House of Dior.