The federal criminal justice system works a little differently than that at the state level. To begin with, federal prosecutors will rarely pick up a case that they cannot win. They will usually let the state handle the case.
If the federal prosecutor looks over your case and feels he or she can win, then the United States Department of Justice explains he or she will take your case, including any evidence and information gathered, to the grand jury. The grand jury will then decide whether or not to indict you.
Going to grand jury
The U.S. Constitution mandates that all felony charges at the federal level have to go through the grand jury. The prosecutor will prepare for the grand jury as if he or she was going to court. The grand jury is regular citizens called for jury duty. They will look over the information the prosecutor has gathered to determine if it is likely you are guilty of the crime.
You should note the grand jury does not assume your guilt or innocence. It is only determining if the prosecutor has enough evidence against you to build a good case.
If the grand jury decides to indict you, it means the prosecutor will bring charges against you. You will get a notice that explains the charges. At this point, you will have to start preparing to defend yourself in court.
Remember that a federal prosecutor cannot bring formal charges against you until the grand jury indicts you. That is an essential step in the federal criminal justice system.