Homonyms are words that sound alike but have different meanings.
(the county fair, they received fair treatment )

Homophones are a subset of homonyms but have different spellings.
(a pear is a fruit, two shoes make a pair)

Homographs are words that are spelled the same but have different meanings.
(he told a lie, he told the dog to lie down)

Heteronyms are a subset of homographs but have different sounds.
(tear in the eye, tear the paper)