Parallelism is the primary poetic device used in Hebrew Poetry, in which the first and second line of a couplet are placed parallel to each other to form a bicolon. The poetry lies in the extra meaning that can be drawn from the comparison. The book of Job, The Psalms, Proverbs, Ecclesiastes, Song of Songs, the prophets who often spoke in verse, and, well, any poem or song in the Old Testament were built primarily with different kinds of parallelism.

Simple kinds of Parallelism:

• Synonymous Parallelism: Two phrases say the same thing, with similar wording.

  The heavens are declaring the glory of God;
      And the firmament is showing His handiwork.

  Psalm 19:1

• Antithetic Parallelism: Two phrases share the same idea, from both a positive and a negative perspective.

  A wise son brings joy to his father;
      But a foolish son, grief to his mother.

  Proverbs 10:1

• Climactic Parallelism: Similar phrase is echoed in different forms, building to a climax.

  Praise the LORD.
  Praise the LORD from the heavens;
    Praise Him in the heights.
      Praise Him, all his angels;
        Praise Him, all his hosts.
          Praise Him, sun and moon;
            Praise Him, all ye stars of light.
              Praise Him, heavens of heavens,
                And waters that are above the heavens.
  Let them praise the name of the LORD
      For He commanded, and they were created.
  He has established them for ever and ever;
      He has made a decree which shall not pass away.

  Psalm 148:1-6