Definition - What does Grand Jury mean?
A grand jury is a body of individuals who are legally obligated to determine whether criminal charges should be brought against a person. A grand jury differs from a typical trial jury, whose job it is to determine whether a person is guilty or innocent of a crime. Also, unlike a typical trial jury, a grand jury does not typically meet every day.
Justipedia explains Grand Jury
A grand jury hearing is typically only used for high crimes, such as felonies. While many countries held grand jury hearings at one time, the United States is the only country that does currently. The reason for the continuance of this practice in the United States is the Fifth Amendment of the United States Constitution, which stipulates that a grand jury be implemented. However, each state has the freedom to determine how to employ grand juries, so their formation varies from state to state.