The words bard, barred sound the same but have different meanings and spellings. Why do bard, barred sound the same even though they are completely different words?
The answer is simple: bard, barred are homophones of the English language.
One of an ancient Celtic order of minstrel poets who composed and recited verses celebrating the legendary exploits of chieftains and heroes.
A poet, especially a lyric poet.
A piece of armor used to protect or ornament a horse.
To equip (a horse) with bards.
Marked with bars or stripes: barred prison cells; barred plumage on a bird.
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").