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.)