I'll try to answer that, if I may.
Both are creatures of the United Nations. The IPCC was created by governments in about 1988 in order to provide them with authoritative information assessments on the state of knowledge of the science—and I use that word very broadly—of climate change.
Its first assessment was completed in about 1990, and this coincided with a large intergovernmental meeting in Geneva called the Second World Climate Conference. The results of the IPCC's first assessment were presented there and led to the desire to create a negotiating body. This led to the UN Framework Convention on Climate Change.
The second IPCC report was completed in about 1995, and it is probably no exaggeration to suggest that in fact this led and gave a considerable impetus to the completion of the negotiations on the Kyoto Protocol.
The third assessment was completed in 2001, and to some extent it's still a little too soon to understand exactly what the implications of that report will be on the UN framework convention process.
Now we've come to the fourth assessment that will be completed this year, in 2007.