A structural trap is a shape: an anticline, or a block closed against a fault. A stratigraphic trap is a change in the rock: a pinchout, a reef, an unconformity. Either way the container needs reservoir rock and a seal that can hold the column. A closure on a map with no seal is a shape, not a trap.
The trap is not the reservoir. The reservoir is the part of the container that can store and deliver hydrocarbons. A trap can contain reservoir, seal, and water-bearing rock together. The accumulation sits where the reservoir and the closure overlap.