Here's why:
* Homophones sound the same but have different spellings and meanings (e.g., "there," "their," and "they're").
* Homonyms have the same spelling and pronunciation but have different meanings (e.g., "bat" the animal and "bat" the piece of sporting equipment).
"Pair" can refer to two things that belong together (e.g., a pair of shoes) or to the act of matching two things together (e.g., "pair off").