This Pudełko kartonowe icon is made in Material Design style developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 4,300 icons, all in the same style and quality.
A cardboard box is a bunch of rectangles that combine together folding it to mold it as one to make it into a container. On the sides there are small slits that have a handle to grasp it on, these are lines that come to a point in the top-middle of the side rectangles.