The Triple Entente was not a formal alliance, and there were no written agreements between the three countries. However, they did agree to consult with each other on matters of foreign policy, and to provide military support if necessary.
The Triple Entente also had the support of other countries, including Belgium, Luxembourg, and Portugal. These countries were not formally part of the Triple Entente, but they were sympathetic to its aims and were prepared to provide assistance if necessary.
The Triple Entente played a major role in World War I. The war began when Austria-Hungary declared war on Serbia in 1914. Russia, as Serbia's ally, declared war on Austria-Hungary. Germany, as Austria-Hungary's ally, declared war on Russia. France and the United Kingdom, as Russia's allies, declared war on Germany.
The war lasted for four years, and it resulted in the defeat of Germany and Austria-Hungary. The Triple Entente was victorious, and it helped to establish the peace settlement that was agreed at the Treaty of Versailles.