The CanvasImageSource
type represents any object of one of the following type: {{domxref("HTMLImageElement")}}, {{domxref("HTMLVideoElement")}}, {{domxref("HTMLCanvasElement")}}, {{domxref("CanvasRenderingContext2D")}}, or {{domxref("ImageBitmap")}}.
It doesn't add any property or method to them, it just act as a generic name where any object implementing one of these interfaces can be used, like the {{domxref("HTMLCanvasElement.createPattern()")}} or {{domxref("HTMLCanvasElement.drawImage()")}} methods.