A stanza is a section in a poem separate from other sections in the work. It is always made up of two or more lines of poetry. For the most part, stanzas within a poem are all the same length and will follow in both meter and rhyme. Their function is to work similarly to paragraphs in non-poetic works, providing readers with a new topic in each one, yet one that connects it to the entire work.
Stanzas sometimes only have two lines. In this case, it is called a couplet. Couplets almost always rhyme in poems since they stand apart and alone. This is the minimum number of lines that can be found in a stanza.
When finding poems greater than two lines, there are two kinds that make up stanzas. The first is called a tercet. The tercet stanza exists when it contains only three lines of poetry. Unlike the couplet, tercets do not follow rhyme regularly, although they can rhyme as well. Three lines rhyming is called a triplet.
Finally, stanzas can contain four lines of poetry. Like the tercet, these can follow a rhyme scheme, but they do not have to rhyme. The only significant element in this type of stanza is the number of its lines.