"Richard Cory" by Edwin Arlington Robinson is a "narrative poem." The term "narrative poem" is used to describe a genre of poetry that tells a story. Although the work is formally a poem, in terms of content, it resembles a short story with a first person plural narrator who observes Cory's exterior actions but has no access to Cory's private thoughts or emotions.
In terms of poetic structure, the poem consists of four four-line stanzas. The stanzas are rhymed "ABAB," a form known as "open quatrains." Although this is the same rhyme scheme as is used in "common meter," the lines are iambic pentameter, rather than the alternating tetrameter and trimeter of common meter. Nonetheless, the rhyme scheme produces some of the effect of a ballad, a traditional type of narrative verse. The rhymes are regular masculine rhymes and most of the lines are end-stopped rather than enjambed.
The form of all the lines in the poem is "iambic pentameter." This means that each line consists of five iambic "feet." In other words, the smallest repeated rhythmical unit is an iambic foot consisting of an unstressed syllable followed by a stressed syllable, and this pattern is repeated five times (thus "pentameter").