The past international associations of communist organizations were each called an “International.” Three Internationals have existed, which corresponded to the three great quantitative stages in developing the industrial revolution and the transition from agriculture to industry. Each of these stages produced its corresponding doctrines of the class struggle, which served as the foundation of each successive Communist International.
Lenin’s history of each of the three Communist Internationals serves as an introduction.
The First International (1864–72) laid the foundation of an international organization of the workers for the preparation of their revolutionary attack on capital. The Second International (1889–1914) was an international organization of the proletarian movement whose growth proceeded in breadth, at the cost of a temporary drop in the revolutionary level, a temporary strengthening of opportunism, which in the end led to the disgraceful collapse of this International.
The Third International actually emerged in 1918, when the long years of struggle against opportunism and social-chauvinism, especially during the war, led to the formation of Communist Parties in a number of countries. Officially, the Third International was founded at its First Congress, in March 1919, in Moscow. And the most characteristic feature of this International, its mission of fulfilling, of implementing the precepts of Marxism, and of achieving the age-old ideals of socialism and the working-class movement—this most characteristic feature of the Third International has manifested itself immediately in the fact that the new, third, ‘International Working Men’s Association’ has already begun to develop, to a certain extent, into a union of Soviet Socialist Republics.
The First International laid the foundation of the proletarian, international struggle for socialism.
The Second International marked a period in which the soil was prepared for the broad, mass spread of the movement in a number of countries.
The Third International has gathered the fruits of the work of the Second International, discarded its opportunist, social-chauvinist, bourgeois and petty-bourgeois dross, and has begun to implement the dictatorship of the proletariat.
(V. I. Lenin, The Third International and Its Place in History, 1919.)
http://www.marxists.org/archive/lenin/works/1919/apr/15.htm
A rogue “Fourth International” was formed in 1938, and the Communist Information Bureau was formed in 1947.
Marxist Glossary Expanded Edition 3.0 can be found on MARS website at the Marxist Glossary for the 21st Century page. Also can be downloaded from the files of the Marxist Glossary Discussion group Facebook page.