This Beta 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 4,300 icons, all in the same style and quality.
Its an image of the Greek letter beta. It a B shape with rounded corners, that is two lines thick. The back of the B is extended slightly beneath the letter, almost like a comma hanging off the bottom.