US Elections How do they work : U S presidential elections easily explained

1. How many houses does the US Congress have?
2. Are there public elections for both of them?
3. What is thr role of the President?
4. What is the House of Representatives for?
5. How often are the members of this branch elected?
6. What does the number of representatives depend on?
7. Who elects the Senators?
8. How many senators does each state have?
9. How often do the Americans choose their leader?
10. Who do the citizens wote for?