Streaming
Streaming continuously captures images from a source and presents them at a target. In BetterDisplay, the source can be a display or a window, and the result can be shown on another display or in a picture-in-picture window.
The source and target have separate roles. Cropping selects a source region. Scaling fits the captured image to the target. Filters change its appearance. Capturing and showing the image this way differs from macOS display mirroring and can introduce latency.
Here, streaming need not mean broadcasting over the internet. Capture requires the appropriate macOS Screen Recording permission. See Stream Display, Window Stream and Picture in picture.