A question from Yahoo! Answers:

How does a federal government differ from a unitary or confederate system of government?

In a unitary system, there are no sub-national units that have legislative power; all law is national.

In a federal system, there are sub-national units with legislative power, but national law takes precedence (for example, in the U.S., federal law normally takes precedence over state law).

In a confederate system, there are sub-national units with legislative power, and sub-national law normally prevails (for example, in Switzerland, the national laws are effective only after they are ratified by each canton; if even one canton rejects a law, it does not become effective).