This is the famous balcony scene when Romeo jumps the wall into Juliet's orchard after they have met at the party. He is already in love with her (or in lust at this point) and uses a metaphor to compare Juliet's beauty to the brightness and radiance of the sun. The sight of her brightens his life just as the sun brightens the day. The East, of course, refers to the fact that the sun rises in the east. The theme of light and dark is used throughout the play to symbolize happiness and sadness and good and bad.
In this scene (Act II.ii), Romeo is hiding in the Capulet's orchard the morning after the party, and happens to see Juliet framed by the window. Romeo is speaking in metaphor in these lines, comparing the window to the East, and Juliet to the sun (after all the run rises in the East). He is breathless with her beauty, and struck anew by his love for her. And while he is talking to himself, he continues the conversation, basically asking the universe to move her into a better view. Essentially, this entire scene is about Romeo mooning over Juliet in infatuation, but those first few lines are metaphorical, comparing Juliet to the radiance of the sun.