Felony defendants are usually brought to federal court in the custody of federal agents. Usually, the charges against the defendant are in a criminal complaint. The criminal complaint is accompanied by an affidavit that summarizes the evidence against the defendant.
At the defendant's first appearance, a defendant appears before a federal magistrate. This magistrate will preside over the first two or three appearances, but the case will ultimately be referred to a federal district court judge (more on district judges below).
The prosecutor appearing for the government is called an "Assistant United States Attorney," or "AUSA." There are no District Attorney's or "DAs" in federal court. The public defender is often called the Assistant Federal Public Defender, or an "AFPD."
When a defendant first appears before a magistrate, he or she is informed of certain constitutional rights, such as the right to remain silent. The defendant is then asked if her or she can afford counsel.
If a defendant cannot afford to hire counsel, he or she is instructed to fill out a financial affidavit. This affidavit is then submitted to the magistrate, and, if the defendant qualifies, a public defender or CJA panel counsel is appointed. The affidavit is submitted under the penalty of perjury, and must be complete.
After counsel is appointed, the magistrate informs the defendant of the charges and the statutory maximum sentence. The "statutory maximum" is the most jail time that a defendant can receive -- it is rarely the actual sentence that is given.
The magistrate then turns to the issue of release, or bail.