The words tacked, tact sound the same but have different meanings and spellings. Why do tacked, tact sound the same even though they are completely different words?
The answer is simple: tacked, tact are homophones of the English language.
Simple past tense and past participle of tack.
Acute sensitivity to what is proper and appropriate in dealing with others, including the ability to speak or act without offending.
Archaic The sense of touch.
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").