The term of a federal judge according to Article III of the Constitution, is for life. The President nominates a judge and it is confirmed by the Senate.
The Constitution has no specific requirements for those who will become a federal judge. Congress, however, typically recommends potential nominees along with the Department of Justice. They review these nominees' qualifications and have their own informal criteria that they use to judge. The duties are given to the judges by the district court. The duties tend to vary depending on the court the judge is in. There are 13 courts of appeals.