Socialism is Worker Ownership of the Means of Production. There sre many, many forms, such as Anarcho-Syndicalism, Marxism-Leninism, Democratic Socialism, Market Socialism, Libertarian Socialism, Anarcho-Communism, Council Communism, Left Communism, and more.
Communism is a more specific form of Socialism, by which you have achieved a Stateless, Classless, moneyless society. Many Communist ideologies are transitional towards Communism, such as the USSR's Marxism-Leninism or China's Dengism and Maoism.
Whether by reform or Revolution, the form doesn't change.