The words whine, wine sound the same but have different meanings and spellings. Why do whine, wine sound the same even though they are completely different words?
The answer is simple: whine, wine are homophones of the English language.
To utter a plaintive, high-pitched, protracted sound, as in pain, fear, supplication, or complaint.
To complain or protest in a childish fashion.
To produce a sustained noise of relatively high pitch: jet engines whining.
To utter with a whine.
A beverage made of the fermented juice of any of various kinds of grapes, usually containing from 10 to 15 percent alcohol by volume.
A beverage made of the fermented juice of any of various other fruits or plants.
Something that intoxicates or exhilarates.
The color of red wine.
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").