The words praise, prase, prays, preys sound the same but have different meanings and spellings. Why do praise, prase, prays, preys sound the same even though they are completely different words?
The answer is simple: praise, prase, prays, preys are homophones of the English language.
To extol or exalt; worship.
Expression of approval, commendation, or admiration.
The extolling or exaltation of a deity, ruler, or hero.
Archaic A reason for praise; merit.
A light green or light grayish-green variety of translucent chalcedony.
Third-person singular simple present indicative form of pray.
Third-person singular simple present indicative form of prey.
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").