There are 2 circular lines following each other with an arrow on the ends of the circular lines. The are working together as a revolving circle to complete a rotation.
This Synchronize 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.