Idea of 1st Icon
It's an icon of a number one enclosed in a circle. The number is circled, possibly to indicate that a list will follow or a question may follow the icon. The icon is entirely black and white.
This 1st 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 6,200 icons, all in the same style and quality.