The Triple Entente was an alliance
between the three Great Powers
, and Great Britain
Great Britain, fearing Germany as a rising naval power, allied with France since both nations opposed the German support of the Boers: this was known as the Entente Cordiale and was negotiated in 1904. France had made a military alliance with Russia in 1894 (the Dual Alliance), so in 1907 Russia joined the Entente Cordiale and the Triple Entente was formed. This alliance countered the Germany-Austria alliance and the Entente Powers became three of the major Allied Powers when World War I began.
It was because of the Entente that all three nations entered the war to oppose Germany.