The words days, daze sound the same but have different meanings and spellings. Why do days, daze sound the same even though they are completely different words?
The answer is simple: days, daze are homophones of the English language.
During the daytime on every day or most days: She works days and sings in a band at night.
To stun, as with a heavy blow or shock; stupefy.
To dazzle, as with strong light.
A stunned or bewildered condition.
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").