Iambic pentameter is one of the most used of all rhythm patterns in English poetry. Five sets of one unstressed syllable followed by one stressed syllable make up one line of iambic pentameter verse. Iambic pentameter refers only to the rhythm of the language being used. It has nothing to do with any rhyme scheme that may or may not be present. Examples of this pattern in use could include many of the writings of William Shakespeare. In the quotes below, the bold syllables are stressed - five pairs of unstressed and stressed syllables in each line.
"If music be the food of love, play on" (Twelfth Night, Act 1 Scene 1)
"Thou art thyself, though not a Montague." (Romeo and Juliet, Act 2 Scene 2)
"Who is it in the press that calls on me?" (Julius Ceasar, Act 1 Scene 2)
Iambic pentameter is 10 syllables in each line throughout a poem, not 5.