Iambic pentameter is a rhythmical pattern of syllables. The "iambic" part means that the rhythm goes from an unstressed syllable to a stressed one, as happens in words like divine, caress, bizarre, and delight. It sounds sort of like a heartbeat: daDUM, daDUM, daDUM. The "pentameter" part means that this iambic rhythm is repeated five times, or has five feet: daDUM daDUM daDUM daDUM daDUM[da].

Shakespeare's Sonnet 97 is held up as an example of perfect iambic pentameter:

XCVII.

How like a winter hath my absence been
From thee, the pleasure of the fleeting year!
What freezings have I felt, what dark days seen!
What old December's bareness every where!
And yet this time removed was summer's time,
The teeming autumn, big with rich increase,
Bearing the wanton burden of the prime,
Like widow'd wombs after their lords' decease:
Yet this abundant issue seem'd to me
But hope of orphans and unfather'd fruit;
For summer and his pleasures wait on thee,
And, thou away, the very birds are mute;
Or, if they sing, 'tis with so dull a cheer
That leaves look pale, dreading the winter's near.

William Shakespeare


ps .. noted those extra two guests at the Black Lion, LH - will be interesting to see what happens next!