Ed laughs. A lot.
He doesn't have one speaking line in the whole movie. It is doubtable that he has said aything in his whole life as a laughing Hyena.
Mostly, he laughs at Banzai. Banzai regularly tries to hurt/mame/otherwise injure Ed - anything to get him to shut up. Again, Mostly, it doesn't work. Ed laughs constantly, and there's nothing another Hyena can do about it.
Lions get a different kind of respect. You won't even hear a nervous giggle out of Ed when faced with a full-grown lion. Not even Shenzi gets this kind of respect, mostly because this kind of respect is laced with terror.
Most people think Ed doesn't have a clue about what's going on. He certainly looks like he just tags along with Shenzi and Banzai just because, by some twisted miracle, he hasn't been killed yet.
However, on occasion, he acts smarter than the rest of them. It is quite possible that Ed laughs because he can't believe how stupid the rest of them are. Ed could be a genious. Sadly, we can never really know the whole story behind Ed - he's too busy laughing.