In "Afterwards," the poem's speaker—a version of the poet—reflects on his own inevitable death, wondering how he'll be remembered once he's gone.
He begins by imagining a time "When the Present has latched its postern" (or back door) "behind [his] tremulous stay." He's personifying time as a figure who has graciously hosted him for his "stay" on earth—his life, which seemed "tremulous" (quivering) due to nerves, emotion, fragility, and/or age—but who will soon enough lock a metaphorical door behind him. Prominent /p/ alliteration ("Present," "postern") pops up here, highlighting the speaker's passage from life to death.
The speaker then imagines that, when he dies, "the May month" will "flap[] its glad green leaves like wings." Here, alliteration ("May month," "glad green," "like leaves") intensifies the lively spring imagery. The speaker will be dead and gone, but the world will go on without him, its beauty as bright and enticing as ever. The simile comparing May's "leaves" to "wings" evokes the lightness and joy of nature's renewal even as the speaker heads into the gloom of death. He adds that these wing-like leaves will be "Delicate-filmed as new-spun silk." Silk is soft and shiny, so this phrasing evokes spring's delicacy and wonder.
In lines 3-4, the speaker wonders whether, after his death, "neighbors" will comment on how he "used to notice such things." He means things like the beauty of springtime and young, green leaves. His question implies that this is how he sees himself—as a "notice[r]" of nature's cycles and the world's beauty—and he hopes that others will remember him this way, too.
Lines 1-4 mark the first of the poem's five quatrains, or four-line stanzas. These quatrains are written in accentual meter—that is, their lines generally contain a set number of stressed syllables (six), but those stresses don't appear in any particular order. Furthermore, lines can contain any number of unstressed syllables, so that overall line lengths vary. Here's line 1, for instance:
When the Present has latched its postern behind my tremulous stay,
This loose rhythm gives "Afterwards" a fairly relaxed, conversational feel, though the poem maintains some structure and musicality. It also follows a conventional ABAB rhyme scheme. (Hardy continued to use meter and rhyme—the standard tools of 19th-century poetry—well into the 20th-century modernist era, when free verse came into fashion.)