District Court: This is like the first round of a tournament where most games are played. It's the trial court level in the federal system where both civil and criminal cases are initially tried.
Court of Appeals: If you disagree with a call made by a referee during your game, you might want to appeal it or ask for it to be reviewed. That's what happens at this level - decisions from district courts can be appealed here.
Supreme Court: This is like the final championship game where ultimate decisions are made. It's the highest court in the land, making final interpretations of federal law and constitutionality.