The words fro, froe sound the same but have different meanings and spellings. Why do fro, froe sound the same even though they are completely different words?
The answer is simple: fro, froe are homophones of the English language.
Away; back: moving to and fro.
A cleaving tool having a heavy blade set at right angles to the handle.
Definitions 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").