From Envirowiki

The Left is a part of the political spectrum that generally includes feminists, socialists, anti-racism groups, environmentalists and other groups. It often includes people who speak out for the voiceless, or the oppressed, against their oppressors. It often has strong values of community, and the power of the masses. The left is more often anti-authoritarian (or liberal) than the Right, however this is not a hard and fast rule by any means, soviet and maoist Communism are examples of authoritarian left government.

The first major leftist movement probably included the french anarchist movement during the french revolution