It is representing the idea of one free. It is made like a medal in the shape of a circle with all kinds of design around it. It looks like an award you would get for winning.
This One Free 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.