what is the branch hear cases about the laws and decides what the laws mean
Generally speaking, the judicial branch interprets the laws. It does not make laws and it does not enforce laws. Instead, it interprets them. In a system like that of the United States, each branch of government has its own function. The legislative branch passes laws. The executive branch enforces them. The judicial branch, by contrast, interprets the laws. What this means is that the judicial branch is the one that decides what the laws mean. When there is a dispute over the meaning of a law (whether it is a law passed by Congress or the Constitution), the judicial branch is asked to decide whose interpretation of the law is correct.