Final answer:
The Triple Alliance was formed by Germany, Austria-Hungary, and Italy, while the Triple Entente consisted of Great Britain, France, and Russia. Italy later switched to join the Entente, and other nations eventually joined the Allied Powers.
Step-by-step explanation:
Triple Alliance and Triple Entente
Before World War I, two major alliances were formed between the great powers of Europe. The Triple Alliance initially consisted of Germany, Austria-Hungary, and Italy; however, Italy switched sides at the onset of the war. In contrast, the Triple Entente was composed of Great Britain, France, and Russia. The assassination of Archduke Franz Ferdinand set off a chain reaction, leading to the declaration of war and the mobilization of these alliances.
Due to a series of side treaties, many smaller nations and other great powers became entangled, leading to the expansion of what were known as the Central Powers and the Allied Powers. The Allied Powers were originally based on the Triple Entente and grew to include nations such as Italy, Japan, Belgium, and eventually the United States.