Double jeopardy means that a person cannot be tried

They cannot he tried for the same crime twice

The Double Jeopardy clause states that a single person cannot be tried for the same crime twice.

If a person goes to court for a crime, and they are either acquitted or convicted, they cannot be tried again for the same exact crime. The court is prohibited from retrying that person, and violates a person's Fifth Amendment right. The law was set in place to prevent erroneous conviction of suspects, consequences of successive prosecutions, and cumulative punishment. It also upholds the integrity of the justice system and finalizes any criminal proceedings.

For example; let's say a man is a suspect in a bank robbery case. He is proven not-guilty by the court and acquitted. If he robs a bank again somewhere down the line, the court cannot try him again for the same crime. Also, the 1999 movie "Double Jeopardy" is all about this clause, and is perfect to watch if you really want to get a solid example of it.