Short answers, pulled from the story.
The Axis powers were a military coalition that fought against the Allies in World War II. Its three principal members were Nazi Germany, the Kingdom of Italy, and the Empire of Japan, united by far-right ideologies and shared expansionist goals, though they lacked deep coordination.
The name comes from a speech by Italian leader Benito Mussolini on the 1st of November 1936, when he announced a nine-point protocol with Germany and declared that other European nations would rotate around a Rome-Berlin axis. Mussolini had first used the word 'axis' in print in September 1923, writing that 'the axis of European history passes through Berlin.'
Germany, Italy, and Japan signed the Tripartite Pact on the 27th of September 1940 in Berlin. Hungary joined on the 20th of November 1940, Romania on the 23rd of November, Slovakia on the 24th of November, and Bulgaria on the 1st of March 1941.
The Axis population in 1938 was 258.9 million, against an Allied population of 689.7 million, a ratio of about 2.7 to 1 in the Allies' favor. Axis wartime GDP peaked at $911 billion in 1941 in 1990 international dollars, while Allied GDP stood at $1,798 billion; the United States alone, at $1,094 billion, exceeded the combined Axis total.
Japan attacked the US naval base at Pearl Harbor on the 7th of December 1941 to disable the American Pacific Fleet and buy time to seize petroleum-rich Southeast Asia. Japan depended on the United States for 80 percent of its petroleum, and a US trade embargo cut off that supply, making continued war in China impossible without a new oil source.
Romania supplied 94 percent of Germany's oil imports in 1940 and 75 percent in 1941, and fielded the third largest Axis army in Europe. General Ion Antonescu was the only foreign leader Hitler consulted on military matters, and the two met no fewer than ten times during the war. Hitler's first admission that the war was lost came after Romania defected from the Axis in August 1944.