Chimera was the special code name given to a project developed by the Tau'ri.
This projection system was Earth's attempt at replicating the holographic technology of the Asgard race. It was an advanced method of creating realistic 3D images which was created virtually. Projections appeared real but were actually created through the use of advanced holographic technology. (SG1: "Covenant", "Bounty")
The first deployment of the system was when Alec Colson attempted to show the world that aliens existed. Lt. Colonel Samantha Carter used Chimera to convince the public that it was simply a hologram in order to hide the discoveries of the Stargate Program. She claimed that the United States Air Force was developing the technology and that it might eventually make it to the civilian field for amusement parks as well as other such attractions. (SG1: "Covenant")
Lt. Colonel Samantha Carter demonstrated Chimera again at a scientific conference where it saved her life as an assassin shot at the hologram revealing his position. She then shot him with the X-699. She officially gave the name Chimera for the technology and highlighted it as a development to the science community. SG-1 then used Chimera to trick and capture Odai Ventrell. (SG1: "Bounty")