The International Space Station (ISS) is an experiment in the design, development, and assembly of an orbital space facility. It serves several purposes:

The ISS is the latest step in both space exploration and living in space. The research being conducted on the ISS is applicable to a variety of scientific disciplines, and is ultimately aimed at improving life on Earth as well as contributing to the eventual journeys man will make to other worlds. There are currently 16 countries are involved in the ISS. (Source: NASA)
A succinct overview of the International Space Station, with information on its international partners, construction, and research goals can be downloaded here.
KS (December 2010)