The words bar, barre sound the same but have different meanings and spellings. Why do bar, barre sound the same even though they are completely different words?
The answer is simple: bar, barre are homophones of the English language.
A relatively long, straight, rigid piece of solid material used as a fastener, support, barrier, or structural or mechanical member.
A solid oblong block of a substance, such as soap or candy.
A rectangular block of a precious metal.
Sports A horizontal bar.
A handrail fixed to a wall, as in a dance studio, used by ballet dancers as a support in certain exercises.
A fingering technique used with fretted stringed instruments in which a finger is laid across the fretboard to stop all or several strings at once.
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").