Idea of Bookmark Icon
The image appears to be a flag or banner. The basic shape is a rectangle with the long sides standing vertically. At the bottom instead of a straight line to close the rectangle the center point of that line dips up like a triangle is missing from the bottom of the rectangle.
This Bookmark 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.