What does the plaintiff do in a court case?

What does the plaintiff do in a court case?
The "Plantiff" is generally the individual (or party) who has brought a case (i.e. suing them, breach of contract, criminal charges, etc.) against another individual (or party), who is referred to as the "Defendant".So if you're suing someone for not paying you for a job you completed, you are the Plantiff, and they are the Defendant.