on Writing Forward site:
Homophones are words that sound alike but have different meanings. Sometimes, they’re also spelled differently: compliment vs. complement.
Since homophones sound the same, they are often misspelled. Sometimes they’re misspelled because the writer doesn’t know there are two different spellings. In other cases, misspelled homophones are the result of typing too fast or failing to proofread carefully.
Spell check will not catch these typos because the spelling is legitimate, even if it’s for a word with a different meaning.