What is fixed fee service?

Could you please elaborate on what a fixed fee service entails? Is it a type of payment arrangement where a client is charged a predetermined amount for a specific service, regardless of the time or resources required to complete it? How does this differ from other pricing models, such as hourly billing or commission-based fees? Could you provide some examples of industries or services where fixed fee pricing is commonly used? Lastly, are there any potential advantages or drawbacks to adopting a fixed fee service model for a business?