The responsibility of the judicial branch is to interpret the laws.
First, let's break down the three branches of government.
The three branches of the US Government are the Executive, Legislative, and Judicial.
Each branch of the government carries out a certain part of the law-making process.
-The Legislative branch (The House of Representatives and the Senate) are in charge of creating laws.
-The Executive (The President and other close advisors) are in charge of enforcing laws.
-The Judicial branch, at a national level, is the Supreme Court. Since courts rule whether or not somebody is breaking the law, it makes sense that the Supreme Court would rule whether or not somebody is going against what the law states. The Supreme Court looks back at the Constitution and decides whether or not something is against what it states, therefore interpreting the laws.
Hope this helped! :)