A more thorough explanation:

Definition: A federation is a group of states, groups, or peoples that are united under a strong central authority, but still have some control over their own local affairs.

For example, the United States is a federation. Each state has its own government and laws, but they are all united under the federal government. The federal government has the power to make decisions that affect the entire country, but the states still have some control over their own affairs.

Another example of a federation is the European Union. The member countries are united under a central authority, but they still have some control over their own economies and laws.

These examples illustrate the definition of a federation because they show how different groups can come together under a central authority while still maintaining some level of autonomy. This allows for a balance of power between the central authority and the individual groups, which can help to prevent abuses of power and ensure that everyone's needs are being met.