A double after partner has opened the bidding and right-hand opponent intervenes with a suit call, to show values and, usually, four cards in an unbid major.
It is for take-out, not penalties. It also goes by the name of Sputnik double because players first used it in 1957, the same year as the launch of the Russian spacecraft, Sputnik.
This hand is suitable for a negative double if partner opens one of a minor and RHO overcalls 1♠, or if partner opens 1♠ and RHO overcalls two of a minor.
At duplicate, negative doubles have become almost universal in this situation.