Hamas owns missiles in Gaza. They fired lots of those missiles into Israel, and before this crisis Iran helped Hamas get bigger missiles that can hit targets as far away as Tel Aviv. This all struck the Israelis as overly aggressive negotiating.
Israel has an ongoing multilayer missile defense program, but they decided to aggressively negotiate right back, launching their own attack into Gaza on November 14th. That attack killed, among other people, the head of Hamas' military forces.
Hamas said this Israeli attack "opened the gates of hell", and they launched some 1500 rockets from Gaza into Israel over eight days. Israel fought right back and hundreds of Palestinians have been killed or injured. Many Israelis died in rocket strikes and bus bombings, Gaza's people need aid and help rebuilding, and the peace process has moved backwards. Both Israel and Hamas claim they won the fight, but honestly nothing about this has turned out well.
The only good news is the recent ceasefire mediated by Egyptian President Mohammed Morsi. It took effect November 21st and stabilized things, so the good solid citizens involved in that feat deserve to celebrate.
Now, does a ceasefire mean everything's fixed? Well