An iambic line of prose or poetry is one that consists of iambs. Got it? No, well let's try: an iamb is two consecutive syllables where the first is unstressed, the second stresed, as in "de-DUM." It's that simple.
What do you get if you put five iambs together? No, it's not a joke, it's iambic pentameter (penta from the Greek for "five") as in: "de-DUM, de-DUM, de-DUM, de-DUM, de-DUM." It sounds better as: "If MU-/-sic BE / the FOOD / of LOVE,/ play ON." Now that's poetry. If iambic pentameter was good enough for Shakespeare, Milton, and Donne, then maybe you should give it a try.