Some people came to pick up friends, while others came to see them off.
Literal
Friend [object-を] greet [purpose-に] came person [also-も] exist-[if-ば], see-off [purpose-に] came person [also-も] exist.
~もいれば~もいる is a set pattern for 'some...others...' — literally 'if there also exist X, there also exist Y.' Each half contains a relative clause modifying 人. 迎え ('picking up') and 見送り ('seeing off') are the two standard actions at airports and stations.