The title of the Robert Herrick's "To the Virgins to Make Much of Time" suggests several things about the genre and rhetorical situation of the poem.
First, the term "virgin" in the period could mean young woman, unmarried woman, or virgin in the modern sense. In all cases, it suggests those who are not yet fully sexually active.
Second, the use of time in the title suggests that the theme of the poem will be "carpe diem", that as life is short and fleeting it is important to seize upon opportunities as they present themselves.
The form "to virgins" suggests that this poem is structured as apostrophe, or the rhetorical figure of direct address, where the narrator is presented as speaking directly to the virgins of the title.
Finally, there is a tradition of poems in this period which are attempts at seduction based on the argument that because life is fleeting we should claim pleasures when we can, including "To His Coy Mistress" and "The Passionate Shepherd to his Love." The title suggests that this poem belongs to that tradition.