A herald reading in public informs the Roman people of an upcoming visit of Prince Herod to the city. Because of the Prince's visit, Romans are advised to keep their mockery of the Jewish religion to a minimum.
A herald keeps the Roman public up to date with news around the city and the Roman Empire.
The scene introduces the hero of the story, Luke Skywalker. In this scene R2-D2 shows Luke the message from Leia.