Within the vast Star Wars galaxy, every galactic power from the Empire to the High Republic has needed a way to reliably communicate across Star systems. Without some form of communication technology, running a Galactic government, coordinating military assignments, or relaying urgent messages would be logistically impossible. Star Wars characters therefore often use holograms to communicate. As three-dimensional projections of their senders and receivers, holograms functioned like 3D video calls, allowing beings dozens of light years apart to both hear and see each other in real-time.
Source：https://www.cbr.com/star-wars-hologram-technology-explained/
