What's the difference between poetry and prose? One of the differences is line length. Another is the use of poetic devices that heighten the use of language and sound. Rhyme is one of those poetic devices.
Using end rhyme is the most common form of writing rhyming poetry. End rhyme is the use of rhyming words at the ends of the lines of a poem. The use of end rhyme creates what is called a rhyme scheme. The rhyme scheme is the pattern of rhyming words in a poem. If you have a stanza of four lines (known as a quatrain) and the words at the end of the first and the third lines rhyme, and the words at the end of the second and the fourth line rhyme, you have a rhyme scheme of abab. It will look like this:
The sky is blue (a)
The grass is green (b)
My heart's anew (a)
My life's serene (b)
There are other possible rhyme schemes, many of which often sound more sophisticated and more complex or more satisfying, such as abab, cdcd, efef, or abba, cddc, effe. There are even some quite intricate rhyme schemes that are pretty amazing, like Edgar Allen Poe's "The Raven." Check out a few lines:
1) While I nodded, nearly napping, suddenly there came a tapping,
As of some one gently rapping, rapping at my chamber door
...
2) Ah, distinctly I remember it was in the bleak December;
And each separate dying ember wrought its ghost upon the floor
...
3) Eagerly I wished the morrow; - vainly I had sought to borrow
From my books surcease of sorrow - sorrow for the lost Lenore
...
4) So that now, to still the beating of my heart, I stood repeating
'Tis some visiter entreating entrance at my chamber door
...
5) But the silence was unbroken, and the stillness gave no token,
And the only word there spoken was the whispered word, 'Lenore!'
...
6) 'Surely,' said I, 'surely that is something at my window lattice;
Let me see, then, what thereat is, and this mystery explore
...
7) Not the least obeisance made he; not a minute stopped or stayed he;
But, with mien of lord or lady, perched above my chamber door
...
8) Though thy crest be shorn and shaven, thou,' I said, 'art sure no craven,
Ghastly grim and ancient Raven wandering from the Nightly shore
You'll notice many of the pairs of lines have internal rhyming between a middle word and the end word, with those words then rhyming with the middle word of the next line as well. Pretty impressive if you ask me!