What is Iambic Pentameter?

William Shakespeare, date and artist unknown

I heard about iambic pentameter for years before I understood what it meant. I was able to figure out that it had something to do with five (penta), but the standard definition, “in poetry, a metrical pattern in a 10-syllable line of verse in which five unaccented syllables alternate with five accented syllables, with the accent usually falling on the second of each pair of syllables,” just didn’t give me a mental picture of what iambic pentameter really sounded like.

It took a lot of syllable counting and oddly accented reading aloud to understand it fully, but when it clicked it was actually pretty simple. Here is a video that explains it thoroughly and helpfully, using a couple of lines from Macbeth as an illustration.