The words faun, fawn sound the same but have different meanings and spellings. Why do faun, fawn sound the same even though they are completely different words?
The answer is simple: faun, fawn are homophones of the English language.
Roman Mythology Any of a group of rural deities represented as having the body of a man and the horns, ears, tail, and sometimes legs of a goat.
To exhibit affection or attempt to please, as a dog does by wagging its tail, whining, or cringing.
To seek favor or attention by flattery and obsequious behavior.
A young deer, especially one less than a year old.
A grayish yellow-brown to moderate reddish brown.
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.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").