It's a logo of Poster reduced to a sheet of paper. The sheet of paper is slightly bent on the bottom right hand side and has a hole on the top. It looks like a normal poster you would see on a bulletin board.
This Poster 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 5,700 icons, all in the same style and quality.