Since you are unwilling or incapable of educating yourself and using Google, here are some links to help with your education:
What's the Difference Between a Grand Jury and a Trial Jury? - FindLaw
Comparing Trial Juries and Grand Juries
Who serves on a grand jury
These colored sentences are called hyperlinks - when you click on them with your mouse, the information magically pops up on your computer screen.
At that point, you must read, understand, and process the information that you are reading.
These links will show you how different the Grand Jury and trial jury processes really are, contrary to your post that they are the same.
Maybe, just maybe, this will help alleviate your ignorance regarding the US legal system in these 2 areas.
In addition, the slight increase in intelligence will hopefully blossom in your future posting ventures.