What is the primary way banks generate revenue?

What is the term for the difference between the interest rate at which banks borrow money and the rate at which they lend it?

Which of these is a fee charged by banks?

Apart from lending, how else do banks generate income?

What are interchange fees?

How do banks earn from foreign exchange operations?

What is a source of income for banks related to third-party products?

What could potentially negatively impact a bank's earnings?