Hezbollah is a Shia Muslim group based in Lebanon. It is not only one kind of thing, and that is the messy truth: it is an armed force, and it is also a political party that sits in Lebanon’s government and runs schools, hospitals, and other services. Iran has long backed it with money and weapons. It is strongly against Israel, and it has fought wars with Israel; many Western governments list it, or its armed wing, as a terrorist group, while many Shia people in Lebanon see it as a defender. The short dictionary line that it “opposes peace” is too tidy: it opposes peace on Israel’s terms, and it is a real power inside Lebanese life, not a small band hiding in the hills. You will also see the spellings Hizbollah and Hizbullah.