ARAM=All Random All Middle (所有人随机选择英雄,所有人都走中路)
FEEDER means Player Who Dies Easily in a Game in an online gaming context. A FEEDER is a player who repeatedly "Dies Easily in a Game" and thereby feeds the opposition with skills, experience money or other items.
AFK is an acronym that means "away from keyboard." But it's primarily meant to convey that you won't be available at your computer or device for a period of time.