An indictment is a formal accusation charging you with a crime. Just because you’ve been arrested for an offense doesn’t mean you’ve been formally charged. An indictment is a formal charging instrument returned by a grand jury finding that there’s probable cause that you committed an offense.
In federal court as well as in the state of Texas usually all felony offenses must be charged by an indictment. An indictment is basically a piece of paper that gives the person who’s been charged with a crime information telling them what type of offense they’ve been charged with and also the penalties that they may face as a result of that.
Also, you should know that an indictment is not any evidence of a guilt and couldn’t be used by a jury at your trial as evidence of guilt. It’s simply a charging instrument to put you on notice of what the government is saying you did to violate the law.