The Prologue in Act I foreshadows the events to come. The chorus is one person who is the narrator. The Prologue tells that the setting is in Verona and that there is a feud going on between two families. It tells us that "a pair of star-crossed lovers will die." The play is going to be two hours long. Since we are told by the narrator that the lovers are going to die, we have to hope that something would change during the story so the outcome is different. The foreshadowing sets the mood for suspense in what will unfold.
The Prologue in Act II describes what has happened to this point. Romeo has forgotten about Rosaline and moved into love with Juliet. Romeo and Juliet have to sneak in and out of the shadows to be together, but they will also suffer because of their love. It continues to foreshadow the impending doom on the lovers.
Reference: The Language and Literature Book by McDougal Littell
The Prologue in Act I introduces the whole play, basically outlining what will happen. Then Act I proceeds to introduce the characters, conflicts, setting, etc. The Prologue in Act II tells us what is yet to come. Romeo no longer loves Rosaline, but now he loves Juliet. "Alike bewitched by the charm of looks" tells that they are both in love, and their passion is powerful.