The term condensation refers to a variety of techniques whose common element is that they condense a large module for a large algebra to a small module for a small algebra, while retaining enough structure so that easily computed information about the small module yields useful information about the big module.

I shall describe at an elementary level the case where the algebra is a finite group algebra and the module is a permutation module, and if time permits I shall mention more advanced techniques which enable us to calculate explicitly character values of (for example) degree 10⁷ constituents of degree 10⁹ permutation modules.