Idea of Empty Box Icon
It is a 3-dimensional box. The box itself appears to be open and empty, as there are 2 flaps open (one each on the left and right), and you cannot see anything inside the box. There is a horizontal line on the front face of the box, near the top, which indicates a handle.
This page contains the Empty Box vector icon, as well as variations of this icon in different visual styles, and related icons. All icons are in the flat vector style, however, differ by the line thickness, fill, and corner radius.