What is multi-party federation?

I am asked to prepare a write up on Identity Federation. I have nearly completed the write up. There is a term multi-party federation which I am confuesed at. Does it simply mean alloting multiple parties to carry out federation? Or is it a term that requires more research?

I couldn’t see much articles in Google. A Google search for multi party federation returned only one valid result. Rest were regarding politics. Could you enlighten me regarding the topics with some introduction.