A 3D display is a type of display that can show different optical depth at the same time. It does so using depth cues based largely on focus and/or stereopsis.
3D displays can be world-fixed, like mounted on a desk, or they can be head fixed, like built into a VR headset.
There are multiple ways to get a 3D display to show proper focus, thereby giving proper accommodation cues. The two main ways are holographic displays and light field displays. A light field display sends focal stacks of images based on rays to the eye.
Multifocal displays are displays that show multiple focus images at the same time, so that the eye can choose what to focus on.
3D is more than just stereoscopic flat images. For a few hundred years, a thought was that stereoscopic flat images formed all of 3D vision.
Benefits
The benefit of 3D displays compared to traditional displays is that 3D displays allow for illustrating in three dimensions using a new level of the human computer interaction loop.
History
2000 to 2010
Autostereoscopic displays from the year 2000 to 2010 used a set of stereoscopic views that were displayed using parallax barriers.