The words pail, pale sound the same but have different meanings and spellings. Why do pail, pale sound the same even though they are completely different words?
The answer is simple: pail, pale are homophones of the English language.
A watertight cylindrical vessel, open at the top and fitted with a handle; a bucket.
The amount that a pail can hold.
Having high lightness and low saturation.
A stake or pointed stick; a picket.
A fence enclosing an area.
The area enclosed by a fence or boundary.
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").