Rhyming words have the same ending sounds.  Many poems use rhyme, especially at the end of lines.  Poetry does not have to rhyme.

Here are some words that rhyme:

Cat, bat, hat, sat, that...

Words that rhyme are not always spelled the same:

No, go, throw, bow, though, stow, yo-yo...

Here are some rhyming words in a poem by Robert Frost:

Whose woods these are I think I know.
His house is in the village though;
He will not see me stopping here
To watch his woods fill up with snow.

Or from L L  Cool J:

My radio, believe me, I like it loud
I'm the man with a box that can rock the crowd
Walkin' down the street, to the hardcore beat
While my JVC vibrates the concrete

Here is a link to a rhyming dictionary: Rhyme Zone!