Robert Herrick (1591-1674) was an English poet of the "Cavalier" school, which emphasized the ideal of the Renaissance Man, as opposed to that of the earlier Christian chivalry. The phrase "Carpe Diem" is Latin for "Seize the day," which reflects a philosophy of living life fully in the moment while you can, since you will one day be dead. The earliest reference to the phrase is from the Roman poet Horace who used it as the title for one of his poems.
This poem falls within the Carpe Diem philosophy, urging the young women who would be reading it to make the best use of their time, namely, by marrying. Although that may not appear to be the best option to modern readers, in his day, a woman marrying young had the best chance to survive childbirth, enjoy raising her children, and lead a full life. See more critical commentary for this poem at the links: