There are considerable variations between social movements. Many social movements are very small, amounting to no more than a few dozen members, and others might incorporate thousands, even millions, of people. Some movements carry on their activities within the framework of the law of the society in which they operate, others function as illegal or underground groups. In general, however, they tend to be loosely organized and operate outside of the established political framework of a society.
Social movements are usually distinct from formally organized political parties or pressure groups.
Although they may have links with political parties, and they can, in time, go on to form a political party. Thus the distinction between the two can become blurred. Social movements can gradually become formal organizations. The Salvation Army in the UK, for example, began as a social movement but has now taken on the characteristics of a more permanent organization. Reformative movements have limited objectives aspiring to alter only certain aspects of the existing society.