Short answers, pulled from the story.
RDS-1, also called First Lightning, was the Soviet Union's first nuclear weapons test. It was detonated on the 29th of August 1949 at the Semipalatinsk Test Site in the Kazakh Soviet Socialist Republic, yielding 22 kilotons of TNT.
US Air Force WB-29 weather reconnaissance aircraft equipped with special atmospheric filters collected radioactive debris on a flight from Misawa Air Base in Japan to Eielson Air Force Base in Alaska on the 3rd of September 1949. Cross-checking that data with later flights confirmed the Soviet test.
RDS-1 was roughly based on the American Fat Man implosion-type bomb dropped on Nagasaki. Security chief Lavrentiy Beria insisted on the Fat Man design because its reliability was well established, and the Soviets had gathered extensive intelligence on it during World War II.
On the 23rd of September 1949, President Harry S. Truman publicly announced: "We have evidence that within recent weeks an atomic explosion occurred in the U.S.S.R." His statement confirmed the test to the world and triggered a US crash program to develop the hydrogen bomb.
The Soviet Union stockpiled 29 RDS-1 bombs by 1951. A pilot series of five weapons was completed by March 1950, with serial production beginning in December 1951.
RDS-1 was officially an arbitrary designation, but several backronym explanations exist: "Special Jet Engine" (Reaktivnyi Dvigatel Spetsialnyi), "Stalin's Jet Engine" (Reaktivnyi Dvigatel Stalina), or "Russia does it herself" (Rossiya Delayet Sama). The United States assigned it the code-name Joe-1, a reference to Joseph Stalin.