When we think of what constitutes a poem, most will certainly think of certain qualities we generally know about poetry: rime, meter (or rhythm), "rules" about the number of lines or the number of syllables. These are traits of the "closed form" of poetry, poems which (sometimes, mostly) strictly adhere to the "rules" of that form.
For example, a haiku--a centuries old form--has a strict line and syllable count: 3 lines, which follow the following pattern of syllables of 5, 7, 5 for a total of 17 syllables. Like much of oriental design, extraneous and "ornamental" or superfluous elements have been stripped away, only the most essential parts are present: there is no rime at all, however, there are other elements we need to consider. One element you will most often see in haiku is Nature. The moon, water, leaves, flowers, animals, place the reader alongside the poet in combination of another element: observation. This way, the reader "shares" the same experience as the poet without actually having the original "experience." The greater the reader's response to the haiku emotionally, the better the haiku. It is both extraordinarily simplistic (from a structural viewpoint), yet extraordinarily sophisticated from an aesthetic stance.
Odes, while more modern, are generally much more substantial in both form and length. Traditionally, odes are written "about" something specific. Here we have one to a bird, one based on a piece of pottery, and one to another natural element. Most often, odes have a sentimental quality to them, sometimes a melancholy or fond remembrance of things the poet wishes the reader to acknowledge and know. Unlike some other closed form poetry, odes do not necessarily follow a strict stanza (a distinct section of a poem) line count, but they do employ specific riming patterns. For example, in "Ode to a Nightingale," we have eight 10-line stanzas, where a very complex end-rime (rime at the end of a poetic line) scheme is followed. For each stanza, the following rime pattern occurs: A-B-A-B-C-D-E-C-D-E (where each letter denotes a new sound, and where it is repeated). This poem also employs what we call "near" rime, words that don't exactly rime, but are close. For example, "deep" and "sleep" are hard rime, but "die" and "ecstasy" are not.
Take note, as well, of the specific stanza/rime pattern of "Ode to the West Wind." Each section of the poem employs four 3-line stanzas, and a pair of lines (also known as a "couplet") at the end. As you will see, this pattern is the same as another closed form, the sonnet (which we will cover next week). However, this sonnet doesn't strictly follow the pattern of the Elizabethan sonnet or the Italian sonnet, rather, it employs elements of both. That's why this poem is celebrated and one of the finest examples of its kind.