With Prejudice:

If a lawsuit is dismissed "with prejudice," the plaintiff is barred from brining another lawsuit on the same claim or cause.

It means that the lawsuit may not be refiled, and as such, it operates as an adjudication on the merits. The dismissal may be voluntary (that is, the plaintiff dismisses with prejudice when a settlement has been consummated), or it may be involuntary (often as an extreme sanction imposed by the court for disobedience to court orders).

Without Prejudice:

If a lawsuit is dismissed "without prejudice," the plaintiff can refile another lawsuit on the same claim or cause.