If you face criminal charges, you will have the option of selecting a jury trial. A group of your peers will then be the ones to decide your fate. To render a decision, the jury must reach an agreement. In some situations, every jury must agree to the same decision, and if they fail to do so, it may result in a hung jury.
The Fully Informed Jury Association explains a hung jury is the same as a deadlocked jury wherein they cannot come to an agreement to render a decision. If a jury comes into the court and declares it cannot make a ruling in the case, the judge may require them to try again to see if they can overcome the issues and make a decision.
If the jury cannot reach a decision according to the rules of the court, then the judge will declare a mistrial. This does not mean that you are free or that you are not guilty. It means that the prosecution will have to retry the case. Most of the time, the prosecutor will do so, and you will have to go through another trial.
You will likely face another trial, which can be a good thing because your defense team already knows what will happen. The prosecutor will have a more difficult time surprising your defense team with witnesses or other evidence. This enables your team to adjust its case and possibly make changes to strengthen it. For many people, having a hung jury is a blessing because it is a do-over where they can go through the trial again knowing what worked and did not work before.