The words racket, rackett, racquet sound the same but have different meanings and spellings. Why do racket, rackett, racquet sound the same even though they are completely different words?
The answer is simple: racket, rackett, racquet are homophones of the English language.
A device consisting of an oval frame with a tight interlaced network of strings and a handle, used to strike a ball or shuttlecock in various games.
A wooden paddle, as one used in table tennis.
A loud distressing noise. See Synonyms at noise.
A dishonest business or practice, especially one that obtains money through fraud or extortion.
An old wind instrument of the double bassoon kind, having ventages but not keys.
Variant of racket1.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, from Wiktionary, Creative Commons Attribution/Share-Alike License 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").