Federalism is the belief that a country should work as a federation: several states or regions keep some of their own power, and they also share a central government for the things they do together, like the army or the money. The United States is the example people always point to; Germany and Australia work this way too. People who like federalism say it stops one city from bossing the whole land. People who worry about it say the parts can pull in different directions and the centre becomes weak. It is a politics-class word. You will hear it in the news when a country is arguing about how much power the capital should have versus the local governments. Though actually, “the federal government” in US news is just a nickname for that country’s centre — it is not the same thing as federalism, which is the idea itself.