The words spits, spitz sound the same but have different meanings and spellings. Why do spits, spitz sound the same even though they are completely different words?
The answer is simple: spits, spitz are homophones of the English language.
Plural form of spit.
Third-person singular simple present indicative form of spit.
A dog belonging to any of several northern breeds, such as the Pomeranian or Samoyed, characterized by a long, thick, usually white coat, pointed muzzle and ears, and a tail curled over the back.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, 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").