The term "wadge hierarchy" refers to a mathematical concept that describes a sequence of increasingly complex sets of structures. In layman's terms, it means that smaller structures are combined to form larger ones, which in turn are combined to form even larger ones. Synonyms for the term "wadge hierarchy" include the "tower of sets", the "cumulative hierarchy", and the "iterative hierarchy". All of these terms describe the same underlying concept of structures being built upon each other in a hierarchical fashion. Understanding this concept is essential in many areas of mathematics and computer science, as it provides a framework for organizing complex data and algorithms.