FB 2 and other 65,000 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
This particular icon features a square with rounded edges on the left side. There is a curved line that runs from the bottom of the square and underneath it. On the square is the letter F, B and the number 2.