This icon has 3 check marks on top of each other on the left side. To the right of each check mark are 3 horizontal lines. They are not attached, though.
This To Do 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.