The words parol, parole sound the same but have different meanings and spellings. Why do parol, parole sound the same even though they are completely different words?
The answer is simple: parol, parole are homophones of the English language.
An oral statement or utterance: by parol.
Expressed or evidenced by word of mouth; not written.
Law The release of a prisoner whose term has not expired on condition of sustained lawful behavior that is subject to regular monitoring by an officer of the law for a set period of time.
Law The duration of such conditional release.
A password used by an officer of the day, an officer on guard, or the personnel commanded by such an officer.
Word of honor, especially that of a prisoner of war who is granted freedom only after promising not to engage in combat until formally exchanged.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.