What is a grand jury and how does it work?

In this June 21, 2017, file photo, former FBI Director Robert Mueller, the special counsel probing Russian interference in the 2016 election, departs Capitol Hill following a closed door meeting in Washington.

FBI Special Counsel Robert Mueller has impaneled a grand jury in Washington to investigate Russia's interference in the 2016 election, the Wall Street Journal reported Thursday.

The impaneling of a grand jury, the report says, could signal that the investigation into Russian meddling in the election and possible collusion between members of the Trump campaign could be “ramping up.”

"This is yet a further sign that there is a long-term, large-scale series of prosecutions being contemplated and being pursued by the special counsel," Stephen I. Vladeck, a law professor at the University of Texas, told the paper. "If there was already a grand jury in Alexandria looking at Flynn, there would be no need to reinvent the wheel for the same guy. This suggests that the investigation is bigger and wider than Flynn, perhaps substantially so."

The Journal reported that the grand jury has been at work for several weeks.

What is a grand jury and what does it do? Here’s a look:

What is a grand jury?

A grand jury is a group of people impaneled by a prosecutor to examine evidence and decide if an indictment should be brought against someone. The grand jury hears evidence presented by the prosecutor. Grand juries give prosecutors the ability to put witnesses under oath and to subpoena witnesses and documents.

A grand jury does not find guilt or assign punishment.

What is an indictment?

An indictment is a criminal charge against someone.

Is the grand jury we heard about today the only one looking into the Russia investigation?

No. Reuters reported in June that Mueller took control of the grand jury investigation into former national security adviser Michael Flynn, who did lobbying work for a Turkish businessman and did not initially disclose it.

Does that mean charges are coming in the investigation?
Not necessarily and not now. Renato Mariotti, a former federal prosecutor, tweeted that "empaneling a grand jury is an early step, not a late step, in an investigation," and that "it means there is enough evidence to warrant serious investigation. But it (impaneling of a grand jury) does not mean that charges will be sought."

How many people are on a grand jury?

A federal grand jury is usually made up of between 16 to 23 people. Other grand juries are usually made up of six or 12 people.

How many jurors must vote for an indictment for the prosecutor to charge someone?

It does not take a unanimous decision to get an indictment. It does usually take a two-thirds or three-fourths vote to indict.

What happens if they do not indict? Does that mean that no charges will be brought?

A prosecutor can still bring charges if he can convince a judge he has enough evidence to proceed to trial.