They are camped in the Glorieta de Murcia, which emerged from the movement 15M. This movement, which was initially called the "outraged" and that has its origin in Madrid, has been growing. He formed several groups of people and associations, including: Real Democracy Now, Spanish Revolution, Camped.
It arose from the politicians not hear people, the large amount of unemployment (especially among youth) and how governments are controlled by financial markets.
What they ask is so clear as: combating corruption, a more participatory democracy (not only vote every 4 years and politicians use the votes as they please), changing the electoral law (in Spain using the D 'hondt system, a proportional distribution of seats and the seats are not shared by the real number of votes), that financial markets do not control governments, and other claims, that may be more diluted in the whole of this movement.
Here is an article of NewYorkTimes.
Although most camping in Spain and not since last Sunday, there are still some, like the photo, but disappear today.
Tomorrow June 19th, is called a demonstration for throughout Spain to continue claiming.