Well, to understand this poem necessarily inolves some understanding of the word pastoral and how this impacted litreature. The word pastoral comes from the Latin word for shepherd. Pastoral poems are normally based in an idealised countryside populated by handsome shepherds and beautiful young women, all at one with nature. There is always an amusing irony in pastoral poems, as although the characters are theoretically rustic peasants, the language and diction in which they speak indicates that they are highly sophisticated. The majority of pastoral literature expresses a longing for a "golden age" or a simpler lifestyle.
In "The Passionate Shepherd to His Love," therefore, the speaker makes a number of typically pastoral appeals to convince his beloved to live with him and be his love. These range from sitting upon rocks and watching shepherds feed their flocks to the things that he will make his lover:
And I will make thee beds of roses,
And a thousand fragrant posies,
A cap of flowers, and a kirtle,
Embroidered all with leaves of myrtle.
Thus a sensuous and passionate tone is created as the speaker does his best to seduce his lover with the supposed joys that the countryside can offer.