What is a fixed fee project?

Excuse me, could you please elaborate on what exactly is meant by a "fixed fee project"? I'm trying to understand if it refers to a type of project where the cost is predetermined and doesn't fluctuate based on the amount of work involved or the duration of the project. Is this the case, or is there more to it that I should be aware of? Additionally, are there any advantages or disadvantages to opting for a fixed fee project, particularly in the context of cryptocurrency and finance?