Federalism is a system of government with one, strong, central governing authority as well as smaller units, such as states. If the central government grows too strong, then federalism comes closer to a unitary state, where the governing body has supreme authority and dictates how much power the units are allowed to have.
Asymmetric federalism is a federal state where not all the constituent states have the same autonomy. In other words, the division of powers is not symmetrical.
Here are examples:
Now you have some examples of federalism and can see how many different locations use federalism as a system of governing.