Basically the deal is a temporary cease fire that would then allow negotiations for a full ceasefire after that. It's a gamble, but the US seems to think that if they can get the conflict to a very low grade state, they can convince the Israeli's not to go back in. In a vacuum this isn't a terrible strategy, but there is broad public support for the war in Israel and the ruling coalition knows their days are numbered if there is no war. Even a temporary ceasefire is better than nothing though.