Good question!
The Judiciary Act of 1789, officially titled "An Act to Establish the Judicial Courts of the United States," was signed into law by President George Washington on September 24, 1789. In Article III of the Constitution established a Supreme Court, but left to Congress the authority to create lower federal courts as needed.
Now,
What is a Federal court in cases like this?
The federal court system has three main levels: district courts (the trial court), circuit courts which are the first level of appeal, and the Supreme Court of the United States, the final level of appeal in the federal system.
And how many are there in the US?
The United States district courts (one in each of the 94 federal judicial districts, as well three territorial courts) are general federal trial courts, although in many cases Congress has diverted original jurisdiction to specialized courts, such as the Court of International Trade, the Foreign Intelligence, and further more on non-explainable at the moment.
Hope this helped. <3