Parametric design is a design method based on relationships and parameters rather than constants. Parameters can be adjusted by the designer to optimize the design, allowing for a multitude of potential design solutions from a set of rules and parameters defined by the designer. Parametric design enables rapid application of designs through repetition, variation, and rule implementation. It also supports informed design through integration of external data for optimization and analysis of factors like climate, lighting, and structural performance. Software like Grasshopper, Generative Components, and Processing can be used to incorporate parametric methods into architectural design.