A video is a widget for playing video and audio media. Video support is currently experimental and only fully present on macOS and Linux. To use video players, you must first install these dependencies.
For static images, use an image widget instead. For more programmatic control of rendering, use a canvas. For SVG, use an SVG widget.
You can make a new video widget, open a video file, and play it:
Here is a screenshot of the video example: