When climate activists say you should listen to the science they usually refer to reports by the Intergovernmental Panel on Climate Change (IPCC). The IPCC is an Intergovernmental organization (IGO) providing an objective summary of scienctific results regarding climate change, its impacts and its reasons. The simulation of future climate is one fundamental pillar within climate research. But what is behind it? How does the science sector look like? How do we gain these insights, what does it mean? This lecture aims at answering these questions. In particular, it provides an overview about some basic nomenclature for a better understanding of what climate modelling is about. The following topics will be addressed: Who does climate modelling? Which institutes, infrastructures, universities, initiatives are behind it and which are the conferences climate scientists go to. What background do climate scientists have? What is the difference between climate projections and weather predictions? Why is it called a climate projection and not climate prediction? While climate scientists are not able to predict weather at a specific date in a decade, why does it still make sense to propose general trends under certain conditions? What is a climate model, what is an impact model and what is the difference between these? What are components and features of the different kind of models? Here, some examples will be shortly presented (e.g.atmosphere, ocean, land, sea ice). Quite a few models are open source and freely accessible. If there is time I will shortly show you how you could install an impact model (example mHM) on your local PC. How accessible is the data used for the projections for the IPCC reports? Overview over the used infrastructure (for example JUWELS, a supercomputer in Jülich), programming languages, software components