Digital Hologram
A hologram is the projection of a coherent image into physical space. At current technology levels, this is only possible within fixed hardware displays (for applications such as holographic sculptures).
A Digital Holograms is the simulation of a hologram within virtual space. This could include the project of objects (e.g., adding an object mapped into the space within an augmented reality experience) or could be user interfaces (such as the projection of screens into virtual reality or AR space that may replace the need for separate screens as we have with phones and computers).