This NEF 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.
The icon is depicting a sheet of paper. The top right corner is folded down, forming a right triangle pointing inwards towards the center of the paper. The bottom of the triangle is about 1/5 of the way down the page. In the center of the paper are the letters NEF all capitalized.