Someone somebody可以互换,意思是某个人.anyone anybody可以互换,意思是任何人.someone/somebody常用在肯定句或希望得到对方肯定的疑问句中,anyone/anybody常用在否定句和疑问句中.
例：①there's someone at the gate,is it your brother?某个人站在门口,他是你的哥哥吗?
②Is anybody here?有人在吗?