Alliteration is when words start with the same sound:
Sometimes these are in tongue twisters
She sells sea shells on the sea shore
Alliteration also works well with product names like Coca-Cola, Dunkin' Donuts and Krispy Kreme
Some names also use alliteration and to me probably some of the most memorable are Daffy Duck, Bugs Bunny and Wonder Woman.
Quite a few peoples names are Alliterations, Kim Kardashian, Lois Lane, Marilyn Monroe and Ronald Reagan. Sometimes when speaking we put Alliterations in to emphasize something, but it is not common in spoken English
Many well known phases are examples of Alliteration: Busy as a bee, Dead as a doornail, Give up the ghost, Good as gold and Home sweet home and of course these are regularly used in spoken English.