It means that a narrow depth of field achieves a smooth, out-of-focus blur in the background of an in-focus, sharp subject ...
it doesn't actually mean the blurry background itself; rather, it's the quality of that blur, and the out of focus areas in the fore and background of an image. Though some people still use "bokeh ...
Blur the background of an image with Google Photos ... which elements you want to focus and which ones you want to be out of focus. This allows you to blur the unwanted background or foreground.
Also called as Acrylic Blur Effect on Sign-in Screen, the feature delivers a beautiful experience by adding more focus to ... will roll out an option to disable Blurred Background on Login Screen ...
It means that a narrow depth of field achieves a smooth, out-of-focus blur in the background of an in-focus, sharp subject photo. That can be whatever you want it to be.