Holographic communicator

The holographic communicator (holo-communicator or holocom for short) was a communication system which allowed two or more parties to send holographic images to each other, simulating face-to-face interaction.

The technology was first used by Starfleet in 2373, installed on the bridges of ships including the USS Defiant and USS Malinche. A holo-communicator was also installed in Captain Benjamin Sisko's office on Deep Space 9, and at Starfleet Command on Earth. 

During the Dominion War, increased security measures at the Palais de la Concorde led to the decision by the Palais de la Concorde Press Liaison to eliminate in-person press conferences, and instead use holocom technology to allow journalists to attend remotely. This arrangement proved popular enough to continue even after the war. 

Starfleet continued to use holographic communication for larger meetings, such as a briefing held during the Gateways Crisis in 2376, and another following the Borg Invasion of 2381. 

Other races have employed similar technology, including Kurros of the Think Tank and Shinzon of Remus.