The Dominator technology is alien technology used by the Dominators.
Dominator technology was used when the Dominators arrived on Earth, they used a mind control device to take control of Kara Danvers, Sara Lance, Mick Rory, Ray Palmer, John Diggle, Thea Queen, Martin Stein and Jefferson Jackson. However afterwards the heroes are freed from it's control.
Later the Dominators attempted to eliminate all meta-humans on Earth using a meta bomb before they are stopped by the combined efforts of the Legends, Team Flash, Team Arrow, and Supergirl herself, Kara Danvers.
Months later, after the Dominators fled, A.R.G.U.S. kept a piece of their technology for safekeeping and Barry Allen, along with the help of Leonard Snart, steals it and attempts to use it to try to trap Savitar in the Speed Force prison but ultimately fails due to the latter wielding the Philosopher's Stone.