Taken from their website;
What is Polyvore?
Polyvore is the web's largest fashion community site, where users are empowered to discover their style and set trends around the world. With over 15 million monthly unique visitors, Polyvore's global community has created over 44 million sets that are shared across the web. Headquartered in Silicon Valley, Polyvore is funded by Benchmark Capital, Matrix Partners, DAG Ventures, Goldman Sachs, and Vivi Nevo (NV Investments).
Some outfits are created to mimic a celebrities' style or specific outfit, using outfits that the person has found through various price points, quite often at a significantly lower price then the designer duds the celeb was wearing.
Here I have shown an example of a very chic (collage) outfit someone has created. While the bag and shoes may be more then some people can afford the top and pants come in at amazing price points, especially for such a stylish little outfit. Definitely check the website out!