The term fixed form poem, also known as closed-form poem, simply means that the verse follows a specific or fixed way of being written. Examples of this form include sonnets, haikus, villanelles or limericks. These have rigid structures of meters, stanzas and rhyme schemes. An example of a haiku written by Matshuo Basho is: “An old silent pond ... frog jumps into the pond, splash! Silence again."
One of the most famous examples of fixed form is a sonnet written by William Shakespeare: "Shall I compare thee to a summer’s day?/ Thou art more lovely and more temperate:/ Rough/ winds do shake the darling buds of May,/ And summer’s lease hath all too short a date:/ Sometime too hot the eye of heaven shines,/ And often is his gold complexion dimm’d;/ And every fair from fair sometime declines,/ By chance or nature’s changing course untrimm’d;/ But thy eternal summer shall not fade/ Nor lose possession of that fair thou owest;/ Nor shall Death brag thou wander’st in his shade,/ When in eternal lines to time thou growest:/ So long as men can breathe or eyes can see,/ So long lives this and this gives life to thee."
An example of a limerick by Edward Lear is: "There was an Old Man with a beard,/ Who said, 'It is just as I feared!/ Two Owls and a Hen,/ Four Larks and a Wren,/ Have all built their nests in my beard!'"