Words with the same sound, such as "sound", "round" and "pound", all rhyme. You may already be familiar with rhymes if you were taught nursery rhymes at a young age: "Mary, Mary, quite contrary, how does your garden grow?"
Using rhyming words when writing is a quick and easy way to grab a reader's attention. In the past advertisers often relied on a rhyming jingle to sell products and help people to remember what they were being encouraged to buy. Modern advertising relies less on rhyme, probably because those used in the past were fairly unsophisticated and a little bit too similar to nursery rhymes, making it seem as if advertisers were patronising customers.
Where else do we see rhyme? Poetry, of course! And were do we see - or hear - poetry? In songs! Music relies heavily on rhyme, so you are likely to come into contact with this feature of the language every day, even if you rarely read poetry. Rhyme unifies lines and verses and makes work more memorable. It is used in mnemonic devices (i.e. "Thirty days hath September, April, June and November....").
Test your ability to spot rhyming pairs with this quiz on the subject.