A reefer is a powered refrigerated container holding set temperatures from −30°C to +20°C for food, pharma and cosmetics. It costs roughly 50–100% more than dry freight on the same lane, needs power at every stage — vessel, port racks, genset trucking — and books earlier because slots are scarce.
One set-point per box: frozen (−18°C) and chilled (0–4°C) cargo cannot share a container.