"Elegy Written in a Country Churchyard" begins by setting the scene and mood. A "Country Churchyard" is a graveyard—that is, a burial area connected to a church—in a rural area. The speaker is standing in this rural graveyard as the day ends. He describes in simple, clear details the various sights and sounds that mark the end of the day in a rural English village in the mid-1700s: the church bell rings, cows are herded back to the farm, farmers trudge home from the fields, and darkness envelops the land.
This is an atmospheric beginning to a poem that announces itself, from its title, as an "Elegy"—a poem that mourns someone's death. Death is on the reader's and speaker's minds, then, throughout these opening lines. As "the curfew tolls the knell of parting day," it's easy to imagine a funereal sound to these bells. After all, "parting" is often a euphemism for death. The sorrowful-sounding "lowing" of cattle, like the cries of mourners, mixes with the ringing of the bells. And finally "darkness," a classic symbol of death, descends over the world. Everyone has gone home and the speaker is left in isolation, perceiving death everywhere.
By beginning with accurate, evocative descriptions of the natural world, Gray immediately places his poem within a new kind of nature poetry, one that evolved throughout the 1700s. In comparison, much poetry of the time tended to focus on allegory, in which abstract qualities were personified in imaginary scenes. Although Gray will turn to this type of writing in this poem as well, he deliberately begins the poem by describing concrete images in the real world. It's easy to imagine the speaker as a flesh-and-blood person observing an actual scene in this rural village.
At the same time, the poem follows a pretty conventional form: rhymed quatrains, or four-line stanzas, written in iambic pentameter. This means that each line has five poetic feet that follow a da-DUM rhythm. Here's line 1 as an example:
The cur- | few tolls | the knell | of par- | ting day,
The lines rhyme in an alternating ABAB pattern (the rhyme pairs being "day"/"way" and "lea"/me"). The result is that the poem is both very readable and very quotable. (And, in fact, many phrases from this poem have found their way into popular culture, and into other works of art.)