Program simplification is the concept of reducing a program to a more concise form. In some cases, the solution given by a GP algorithm can be hard to understand and interpret due to its redundancy and complexity. In the past, simplification of these programs was tediously done by hand, but there are now algorithms that will automatically simplify these solutions without human involvement.
Autosimplification is a hill-climbing method for automatically simplifying a Push program. More information is detailed in the Orientation/Autosimplification page and in the paper Effective Simplification of Evolved Push Programs Using Simple, Stochastic Hill-climber by Lee Spector.