Idea of Unit Icon
It's four small squares, each sitting on the corner of one large square. The small squares are connected by the sides of the big square, giving it a connected look. Three of the four small squares are not shaded in and the only square that is shaded in is the small square on the bottom left hand corner.
This Unit 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 6,100 icons, all in the same style and quality.