SVG is the ideal classic format. It scales so that you can resize it to any size without any problems without losing quality. PNG are pixel-based formats. This means that by scaling, their icons lose quality. Thus, it is very important to load the right size icons necessary for your project. Compared to JPG, PNG contains transparency information. This way, a PNG icon can be easily added over a colored background without editing it. If you're not sure which format to choose, choose PNG. It's a safe choice.