Alliteration is the repetition of two or more consonant sounds at the beginning of words in the same sentence, and it generally serves to enhance meaning or add emphasis to important words or ideas. It is generally used in poetry, but it can also be used in prose, of course.
Chapter five of The Pearl by John Steinbeck begins with an awful scene between Juana and Kino. She has stolen the pearl and they are about to physically fight over it. In the second paragraph, Kino follows Juana and we read this [bold print added by me to indicate the alliteration]:
...he could hear her quick footsteps going toward the shore. Quietly he tracked her....
In the fifth paragraph, Steinbeck writes about Juana after Kino has beaten her:
Juana, in her woman's soul, knew that the mountain would stand while the man broke himself; that the sea would surge while the man drowned in it.
One more. In the next paragraph, we read this one, describing Juana:
Her back was bent with pain and her head was low.
Notice that, in each of the examples above, the alliterative words are also the most significant words in the sentences, enhancing meaning by adding emphasis.
Examples of alliteration are easy to find, and I would encourage you to find some examples on your own, as well, since alliteration is a common literary device and you will probably be asked to identify it often in your studies.
According the Merriam Webster Dictionary, Alliteration means
: the use of words that begin with the same sound near one another (as in wild and woolly or a babbling brook )
In Chapter 5, theses are a few alliterations from the book "The Pearl" by John Steinbeck.
Greedy fingers went through his clothes,frantic fingers searched him, and the pearl, knocked from his hand,lay winking behind a little stone in the pathway.
The roosters were crowing and the dawn was not far off. Smoke of the first fires seeped out through the walls of the brush houses, and the first smell of cooking corn cakes was in the air.
Crouching in the house of Juan Tomas, they heard the shock go into their neighbors' minds at the news of the broken boat.
For more about "The Pearl" by John Steinbeck, go check out the enotes.com study guide which includes summaries, themes, character analysis, etc.