The words toad, toed, towed sound the same but have different meanings and spellings. Why do toad, toed, towed sound the same even though they are completely different words?
The answer is simple: toad, toed, towed are homophones of the English language.
Any of numerous tailless amphibians chiefly of the family Bufonidae, related to and resembling the frogs but characteristically more terrestrial and having a broader body and rougher, drier skin.
The horned lizard.
A person regarded as repulsive.
Having a toe, especially of a specified number or kind. Often used in combination: an even-toed ungulate.
Driven obliquely: a toed nail.
Secured by obliquely driven nails: a toed beam.
Simple past tense and past participle of tow.
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").