What is a Playblast?
A Playblast, is a viewport render from the active camera, used commonly for previewing Animation, Staging and placement and the population of elements in a scene.
It is a term common to Maya users.
This is not a final render, and elements like NURB curves are also rendered.
You could say a Playblast is a video capture of the viewport.
Below is an example of a Playblast
To create a Playblast in Blender, you can follow this guide.