It depends on who you mean by "we," but in broad strokes the sides for most of WWI were the "Triple Entente" of Britain, France and (until 1917) Russia, who went to war with the "Central Powers" of Germany and Austria-Hungay. Many other nations joined the war during its course, including the United States and Japan on the side of the Entente powers and the Ottoman Empire on the side of the Central Powers.

Is there a particular time period of the war that you're interested in more information about?

The Nazi party was founded in Germany after World War I, and seized power in 1933.