Conformity, or majority influence, is a form of social influence whereby a person or groups behaviour/attitudes are changed to fall in line with the social norms or values of the majority, even when there is no direct request to do so. It can result from real or imagined pressure.
The most superficial type of conformity is compliance. When complying, an individual conforms publically to avoid social disapproval, but maintains their own private opinion. When they have left the situation they revert to their former behaviour/attitude that they privately hold. The deepest and most powerful type of conformity is internalisation. Internalisation involves a permanent change in the individuals behaviour/attitudes, and results from the views being internalised: the individual is persuaded away from their previous view/behaviour and adopts a new one which becomes part of their own value system.