Shakespeares sonnet explanation?

The speaker of the poem addresses his beloved as "Lord," using the medieval or Renaissance language of faithfulness and loyalty from a follower to his lord. Instead of sending an actual person as ambador to express his loyalty and duty, the speaker sends the poem as a "written embage." The speaker explains that he writes poorly ("wanting words") about how much obligation he feels toward his lord, but if his lord has a strong imagination, he can make the words seem better. Until fate or destiny makes the speaker's ability greater and makes his love look better ("puts apparel on my tattered loving") and more deserving of consideration, he won't show himself, but after his love seems more mature and respectable, he will consent to let his lord "prove" him -- that is, test his devotion.