I hope this makes sense to you ....
Iambic pentameter itself 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. Each iambic unit is called a foot. The "pentameter" part means that this iambic rhythm is repeated five times, or has five feet: daDUM daDUM daDUM daDUM daDUM[da].
Here are a few examples of lines written in iambic pentameter:
"Oh, gentle Faustus, leave this damnèd art," Christopher Marlowe, Doctor Faustus, 5.1.37. This quotation comes from a play written, at least somewhat, in blank verse, unrhymed iambic pentameter.
"I waked, she fled, and day brought back my night." John Milton, "Methought I Saw My Late Espousèd Saint", a sonnet using fourteen lines of iambic pentameter.
"But surely Adam cannot be excused," Aemilia Lanyer, Salve Deus Rex Judaeorum, line 777.
"We hold these truths to be self-evident," Thomas Jefferson, "The Declaration of Independence," line 1. "The Declaration of Independence" is a prose work, but who knows if Jefferson intended to make the first line poetic?
The final foot of the line does not have to be on a stressed syllable (daDUM). Shakespeare, among others, often ends iambic pentameter on an unstressed syllable, so that the last foot sounds like this: daDUMda. The ending with the unstressed syllable is more common in Romance languages, such as Spanish and Italian.
I hope this helps.