Models are used to represent real systems in an understandable way. They take many forms. A conceptual model explains the way a system works. In environmental studies, for example, a conceptual model may delineate all the factors and parameters for determining how a particle moves in the atmosphere after it has been released from a power plant. A conceptual model may also help identify the major influences on where a chemical is emitted and how likely it is to be found in the environment. Such models need to be developed to help target sources of data for assessing environmental problems.