The words foaled, fold sound the same but have different meanings and spellings. Why do foaled, fold sound the same even though they are completely different words?
The answer is simple: foaled, fold are homophones of the English language.
Simple past tense and past participle of foal.
To bend over or double up so that one part lies on another part: fold a sheet of paper.
To make compact by doubling or bending over parts: folded the laundry; folded the chairs for stacking.
To bring from an extended to a closed position: The hawk folded its wings.
To bring from a compact to an extended position; unfold: folded the ironing board down from the wall; folded out the map to see where we were.
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.
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").