What Is Iambic Tetrameter?

An "iamb" is a word or set of words that goes 'da-DAH', like "my KNEE",
or "your FACE", or "his DOG", or "come HERE".

Many poems have the same rhythm (beat) in each line, and there are different
rhythms they can have.  I can show you that, if I take a poem you know, and
recite it first with the correct beat, and then with the wrong beat.

Here's the correct beat:
MAH-ree HAD a LIT-tle LAMB its FLEECE was WHITE as SNOW.

For the wrong beat, let's use 'iambs' like I explained up above:
ma-REE had A lit-TLE lamb ITS fleece WAS white AS snow.

If a poem is in the rhythm of "iambic tetrameter", then each line is
made out iambs, and there are 4 of them ("tetra") in each line.

Now I have to try and find an example for you.  Thank you very much.

I'll make one up.  Remember, an iamb goes 'da-DAH":

my DOG came IN-to SCHOOL one DAY
and CHASED the HAM-sters ALL a-ROUND.
the PRIN-ci-PLE came IN-to CLASS
and TOOK my DOG down TO the POUND.

(The dog 'pound' is the shelter for stray dogs.)

The only reason based on my own answer or some of my instinct jack flack up and down and then twist all around before taking his medicine is because the label of his medicine says that you need to shake well before using or before taking it.