The judicial branch makes sure that laws are followed correctly. It consists of the Supreme Court and 13 circuit courts.
The Supreme Court is the highest (most important) court. Its justices, or judges, interpret the Constitution. That means they decide how it applies in specific situations.
There are eight associate justices on the Supreme Court and one chief justice. The justices are appointed by presidents. They serve until they retire or die.
The Supreme Court reviews cases that have been decided in a lower court. Usually, the losing side appeals to the Supreme Court. They hope it will decide differently than the lower court did. In general, the court only hears cases that have to do with federal law or the Constitution.