Before your offense can be brought to justice, the government has to present the evidence it has against you to a large jury.
The grand jury is made up of a group of "normal" people who examine the evidence of your arrest and decide whether the government has "enough" evidence to prove "formal charge".
A large jury does not decide on guilt or innocence.
It is your job to ensure that the government does not bother citizens and arrests them for better or worse.
The grand jury is only asked to answer the following question:
Does the government have enough evidence to make the arrest?
This standard is called the “probable cause”.
In other words, the grand jury must determine whether there are sufficient probable reasons to accuse you of the crime (s) that the government believes you committed.
Once the grand jury has voted in favor of the government, your offenses will be official.
If the grand jury approves the indictment, one speaks of a "true bill".
If the grand jury rejects the indictment, one speaks of a "no bill".
If the Grand Jury does not charge the charge in your case, the government can try again.