And how it guards against tyranny
Federalism is the idea of powers shared between the national and state governments. While the national government deals with issues like going to war and foreign affairs, state government deal with citizen laws like marriage and divorce. This way, if the national government becomes corrupt, they can only do so much without needing control of the state government too.
Checks and Balances
Checks and Balances is a system where each branch has ways to limit the powers of others. For instance, the president can veto a law, but the senate can override the veto. This way, no one branch can get too powerful.
Seperation of powers
Seperations of powers is where all the decision making power is spread between as many people as possible. This way, no one individual or group will have enough power to become a tyrant.
Big states vs. small states
This is where the great compromise comes into play. With proportional representation in the House of Representatives and equal representation in the senate, the big states cannot overpower the smaller states because small states will still have two representatives in the senate, but states with larger populations will also be taken account for in the senate.