One policy covering death and defined serious illness, usually paying out once on the first event.
Combined cover packages life insurance and critical illness cover in a single policy and premium. The structural detail that matters most: on most combined policies the sum assured is paid once — on the first valid claim, whether that is a critical illness or death — and the policy then ends. Separate policies can pay out for both events independently. Whether a combined policy pays once or twice is confirmed in the wording, and the difference changes what the premium buys, so it is worth confirming in writing before relying on both events being covered.