= to put on trial (legal procedure to assess the guilt or innocence of those committing crimes).
When criminals are arrested by the police, they are usually charged with a crime. Then they are sent to court, where they are put on trial (or: they are tried...). After the various procedures of the trial (defence and prosecution lawyers, witnesses, and for more serious trials: a a jury), and, if they are found guilty, then they are sentenced by the judge or magistrate.
I hope this snapshot of the legal process is understandable..