A smaller, straight (non-articulated) truck with a cargo box built onto the same frame as the cab, typically 12-26 feet long. Used for local and regional deliveries that don't need a full tractor-trailer.
A box truck's cargo box sits on the same frame as the cab rather than being towed separately, which is what makes it maneuverable enough for tight urban delivery routes and residential streets a full tractor-trailer can't access. Many box trucks fall under the 26,001-lb gross vehicle weight rating that would otherwise require a commercial driver's license, which is part of why they're a common entry point for owner-operators and small local delivery fleets — though larger models still cross that threshold and need a CDL like any other commercial vehicle.