Indictment is more the formal process of filing charges. When the prosecutors believe they have sufficient evidence to support them in court. They can enlist a grand jury to decide if there is enough evidence to warrant it before hand, but all the grand jury looks for is if they believe there is enough evidence to go to trial, usually used in what expected to be high profile cases not always used.

Arraignment is the formal procedure for the defendant to enter his plea with the judge.