Idea of Restore Window Icon
There is a square with two other squares overlapping each other in the center of it. The two overlapping squares also have a line towards the top of them. The square to the right is overlapping and higher than the one on the bottom and left.
This Restore Window 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 6,200 icons, all in the same style and quality.