The pixel grid of a display/screen and an image is limited. Many screens have a resolution of e.g. 1920x1080 or 3840x2160 pixels. That means that only a limited amount of color points can be shown on that display which is the amount of pixels that are built in it.

For graphics a pixel based format is standard for e.g. photographies as only pixel data was collected by the camera. The problem with pixels is that the saved information is also limited. It is not possible to zoom infinite into a pixel based image. Vector-based on the over hand have the advantage that zooming is infinitely possible. Therefore this file format should be considered at all times!