The words racks, rax, wracks sound the same but have different meanings and spellings. Why do racks, rax, wracks sound the same even though they are completely different words?
The answer is simple: racks, rax, wracks are homophones of the English language.
Plural form of rack.
To stretch; stretch out.
To reach out; reach or attain to.
To extend the hand to; hand or pass something.
To perform the act of reaching or stretching; stretch one's self; reach for or try to obtain something
Plural form of wrack.
Definitions 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").