Most often, a fee is a payment for a service, both basic - for example, mowing the lawn, and complex - such as drafting a will or preparing taxes.
Sometimes more than one fee is charged for a service (for example, buying a plane ticket for X amount of money, but receiving fees for baggage and transportation costs).
There are state (local and federal) fees associated with obtaining a license such as a driver’s license or passport.
Fees can add up quickly, for example, credit card companies often charge high fees for late payments.
Some services use hidden charges to supplement their bills with unexpected charges. By asking about hidden fees (or just non-obvious fees), you can save yourself a higher bill than expected.