The icon is shaped like a circle but the top right corner of it doesn't fully connect. At the center of the circle is a check mark. The end of the check mark sticks out the opening in the circle a bit.
This Checked 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 6,000 icons, all in the same style and quality.