Internal rhyme is a poetic device involving rhyming words that occur within a line or lines of poetry, sometimes entirely apart from the end-of-the-line rhyme scheme. "The Raven" by Edgar Allen Poe uses internal rhyme in many places, most famously in its first line: "Once upon a midnight dreary, as I pondered weak and weary, over many a quaint and curious volume of forgotten lore..."
Internal rhyme is sometimes called middle rhyme because poets commonly rhyme the middle word with the end word of a line, but many varieties exist. "The Raven" uses internal rhyme in a number of different ways. In the line: "While I nodded, nearly napping, suddenly there came a tapping, As of someone gently rapping, rapping at my chamber door," the repeated sounds set up a dreary, plodding rhythm that underlines the somber mood of the poem.
Internal rhymes are quite common in songs. The Beatles song 'Hey Jude" rhymes middle words from successive lines: "Hey Jude, don't make it bad. Take a sad song, and make it better. Remember to let her into your heart, then you can start to make it better."
Rappers often make use of internal rhyme to create rhythmic variation, such as in this example from the Sugar Hill Gang's "Rapper's Delight": "I'm 6-foot-1 and I'm tons of fun and I dress to a T, you see, I got more clothes than Muhammad Ali and I dress so viciously."