Johan Bijnens Eta and Eta' decays and what can we learn from them? Talk presented at the Eta'05 Workshop on production and decay of eta and eta' mesons 15th--18th September 2005, Jagellonian University, Cracow, Poland Abstract In this talk a short overview of $\eta$ and $\eta'$ decays is given with an emphasis on what can be learned for the strong interaction from them. The talk consists of a short introduction to ChPT, a discussion of $\eta\to3\pi$ beyond $p^4$ and some of the physics involved in $\eta'\to\eta\pi\pi,3\pi$ as well as an overview of anomalous processes. LU TP 05-42, hep-ph/0511076