The words phlox, flocks sound the same but have different meanings and spellings. Why do phlox, flocks sound the same even though they are completely different words?
The answer is simple: phlox, flocks are homophones of the English language.
Plural form of flock.
Third-person singular simple present indicative form of flock.
Any of various North American plants of the genus Phlox, having opposite leaves and flowers with a variously colored salverform corolla.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, 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.