Idea of Invert Selection Icon
It is a square with a circle inside it. The square has a diagonal line from the bottom-left corner to the top-right corner that splits the square and circle into two triangles with half-circles inside them. The top-left triangle is filled with dots outside of the half-circle, whereas the bottom-right triangle is only filled with dots inside the half-circle.
This Invert Selection 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.