The duty to defend is broader than the duty to indemnify, and that single sentence decides more insurance disputes than any other rule in the field. This article explains why the two duties diverge, how courts compare a complaint to a policy under the four-corners rule, and why the Texas formulation calls the same exercise the eight-corners rule. It maps the deep and consequential split over extrinsic evidence, including the narrow exception the Texas Supreme Court adopted in BITCO General Insurance Corp. v. Monroe Guaranty Insurance Co., and it explains what happens when a complaint pleads only uncovered theories but the known facts suggest a covered one. Later sections cover the reservation of rights and the independent counsel that a genuine conflict can require, the consequences an insurer faces for refusing a defense outright, the contested question whether an insurer may recoup defense costs it spent on uncovered claims, and the strategic race to file a declaratory judgment action. The article closes on the point where a defense dispute quietly becomes a bad faith case: the unaccepted policy limits demand and the excess judgment that follows.