Hezbollah has certainly committed terrorist acts, to declare them a "terrorist organization" is probably an oversimplification. For example, unlike Islamic Jihad or even Hamas, they haven't launched suicide attacks inside Israel that I'm aware of, certainly not recently.
They've launched rockets into Israel, Israel has dropped bombs on Lebanon.
They've captured Israeli soldiers, the Israelis have captured Hezbollah guerillas.
They are not a terrorist organization in the sense that Al Quaeda or Islamic Jihad is: the vast bulk of Hezbollah's political organization is not an
armed force. They are a political party, a social services organization, a guerilla army, and yes, a terrorist group, all rolled into one. To imagine
that they're a single purpose terrorist group, though, is to seriously underestimate them.