Suprasegmental features are things such as stressed syllables, tone, pitch, intonation. In poetry, the pattern of stressed and unstressed syllables gives you the rhythm and meter of the poem. In that case, a knowledge of suprasegmentals (or prosody) helps in determining the structure and cadence of the poem. Changing the stress on syllables can also change or alter the meaning.
If the rhythm and meter is not obvious, especially in cases with more modern poetry, the function of suprasegmentals is usually up to the reader. In this respect, modern poetry lends itself to more interpretations than classically structured poetry.
In linguistics, (this includes poetry, prose and the spoken word or language in general), knowledge of suprasegmentals can also help in determining meaning and context. For example, in some languages there are words which are spelled the same but pronounced differently. “Read” is the past tense of “read.” This is an obvious example of pronunciation. In Spanish, término means “term.” But termíno means “I terminate.” So, different stresses and accents can change meaning.
Tone, pitch and stress can clearly affect the meaning of a statement in audible speech as well. “They fooled me, Jerry!” The speaker is upset that he was fooled. “They fooled me, Jerry!” With the stress on “me,” the speaker is more surprised that he was fooled, giving the indication that he has a high opinion of himself and prides himself on not being fooled.