Icon are:

Scalable Vector Graphics $($SVG$)$ which you can rotate, resize and recolor with no loss of image quality, regardless of the size.

Modeled Computer Graphics $($MCG$)$ which you can rotate, resize and recolor with no loss of image quality, regardless of the size.

Normalized Computer Graphics $($NCG$)$ which you can rotate, resize and recolor with no loss of image quality, regardless of the size.