SVG
A picture stored as shapes and lines instead of pixels, so it stays sharp at any size.
See it in SVG path animator. Pick a preset, then press Download SVG.
In plain words
Most pictures are grids of pixels, and they go blocky when enlarged. An SVG file stores instructions instead, such as draw a circle here, this wide, in this colour. The screen follows those instructions at whatever size it needs. So logos and icons in SVG look sharp on a watch or a billboard. SVG is text, so it can be edited and animated with code.