The words brae, bray sound the same but have different meanings and spellings. Why do brae, bray sound the same even though they are completely different words?
The answer is simple: brae, bray are homophones of the English language.
Scots A hillside; a slope.
To utter the loud, harsh cry of a donkey.
To sound loudly and harshly: The foghorn brayed all night.
To emit (an utterance or a sound) loudly and harshly.
The loud, harsh cry of a donkey.
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.