Alliteration is when a sentence or phrase has many words that start with the same sound. It is commonly used in advertising, poetry, headlines, and tongue-twisters. Basically the first consonant repeats itself throughout the sentence.

Alliteration is common for poetry. It was used one thousand years ago in Anglo-Saxon poems. A fine example is a strophe from The Rime of the Ancient Mariner by Samuel Taylor Coleridge:

 The fair breeze blew, the white foam flew,
 The furrow followed free;
 We were the first that ever burst
 Into that silent sea.

Robert Browning used alliteration many times, too. he employed it in the poem Summum bonum. This is a Latin expression and means "all the best".

 All the breath and the bloom of the year in the bag of one bee:

Alliteration is most commonly used in modern music but is also seen in magazine article titles, advertisements, business names, comic strip or cartoon characters, common sayings, and a variety of other titles and expressions.

One example of alliteration is "Sally sold sea shells by the sea shore". In Death Note, the pseudonym of the detective, L, is Ryuzaki Ryuga, his real name is L Lawliet.

Often, characters in books are named with alliteration. Many names in Harry Potter feature alliterations (for example, Godric Gryffindor, Helga Hufflepuff, Rowena Ravenclaw, and Salazar Slytherin). Similarly, in Hairspray, most characters' names feature alliterations (e.g. Tracy Turnblad, Link Larkin, Corny Collins, Dan Dougherty, Penny Pingleton, and Seaweed Stubbs).

Titles of books sometimes use alliteration, including the titles of all thirteen books (except the last one) in Lemony Snicket's A Series of Unfortunate Events. Author Jeff Lindsay's novels about serial killer Dexter Morgan all feature alliteration in their titles: for example, Darkly Dreaming Dexter. Another example is William Shakespeare's Love's Labour's Lost.

A common application of alliteration is in books intended for children learning about letters. Animalia by Graeme Base famously applies alliteration within a storybook, going in order through each letter of the English alphabet and providing many sentences with alliteration.
Places in books: Bat Barn, Terror Tombs, Vampire Village, etc.
Code names: The release names of the Linux distribution, Ubuntu (e.g. Breezy Badger, Hoary Hedgehog, Feisty Fawn, etc.).
Game Titles: Prince of Persia (also the tag: Prince of Persia – Warrior Within).

Brand Names and Alliteration
Companies company use this alliterative effect all the time. The major reason companies use this technique is to ensure that their brand name is memorable. Think, for example, of all of the famous and well known brands and companies that have used alliteration in their names:

•Dunkin’ Donuts
•PayPal
•Best Buy
•Coca-Cola
•LifeLock
•Park Place
•American Apparel
•American Airlines
•Chuckee Cheese’s
•Bed Bath & Beyond
•Krispy Kreme
•The Scotch and Sirloin
Famous People and Alliteration
Alliterative names can also help you stand out in the crowd and can make you more memorable. For example, both fictional characters and real people may stand out in your head as a result of the alliterative effect of their name. Think of:

•Ronald Reagan
•Sammy Sosa
•Jesse Jackson
•Michael Moore
•William Wordsworth
•Mickey Mouse
•Porky Pig
•Lois Lane
•Marilyn Monroe
•Fred Flintstone
•Donald Duck
•SpongeBob SquarePants
•Seattle Seahawks
•Katie Courec (Remember, alliterative words don’t even necessarily have to start with the same letter, they simply have to have the same first sound).
 Pier Paolo Pasolini

Phrases and quotes
Finally, many famous phrases, quotes and saying also make use of alliteration:

•Busy as a bee
•Dead as a doornail
•Get your goat
•Give up the ghost
•Good as gold
•Home sweet home
•Last laugh
•Leave in the Lurch
•Living the life
•Look to your laurels
•Mad as a March hare
•Make a mountain out of a molehill
•Method to the madness
•Moaning Minnie
•Neck and neck
•Not on your nelly
•Out of order
•Pleased as punch
•Pooh-pooh
•Primrose path
•Right as rain
•Right roughshod
•Round Robin

Alliteration is commonly used since it adds interest to a sentence and can be a great way to help you remember names and phrases that you might other wide forget. Enjoy alliteration. It is a very fun and useful literary device.

References 

Figures of speech