The words road, rode, rowed sound the same but have different meanings and spellings. Why do road, rode, rowed sound the same even though they are completely different words?
The answer is simple: road, rode, rowed are homophones of the English language.
The surface of a road; a roadbed.
A course or path: the road to riches.
An open, generally public way for the passage of vehicles, people, and animals.
A railroad.
Past tense of ride.
Nautical A cable, chain, or rope, especially one attached to the anchor of a small boat.
Simple past tense and past participle of row.
Formed into a row, or rows; having a specified number of rows.
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").