In short, the task of the IPCC is analyze scientific information with regards to human induced climate change, the impacts of such human induced climate change, and possible options for adaptation and mitigation.
Seem a little abstract? Well, essentially, the IPCC looks over the scientific literature out there, the most recent and thorough resarch related to climate change. They then analyze it to see how much of any climate change is possibly human induced, and any possible effects that this will have. Then, they try and figure out what can be done, either by adapting to these new changes, or by trying to lessen the effects of climate change.
While it is scientific in nature, the IPCC does not carry out its own independent research. Instead, the committee of scientists and other specialists publishes a special peer- and government-reviewed meta assessment reports based on thousands of scientific reports from around the world on a variety of subjects related to climate. It attempts to carry no bias as in the scientific tradition, looking for the truth and only truth in a subject often laced with poor, end-based science and political hysteria.
Thus, they look at both environmental considerations for the good of the planet, and the intertwining socioeconomic considerations for the good of the human race, making their research multidisciplinary and multifaceted—and multitasking. Both the politicians who make the policies and the scientists who do the research find the IPCC to be a valuable guiding light when it comes to climate change.