Final answer:
Social movements are purposeful, organized groups that arise when justice, fairness, and equality are threatened. They provide an alternative means of political expression and potential influence.
Step-by-step explanation:
Social movements are purposeful, organized groups striving to work toward a common social goal. They typically arise when justice, fairness, and equality are threatened or perceived to be threatened. These movements can take various forms, including protests, campaigns for specific reforms, and calls for revolution.
They provide an alternative means of political expression and potential influence when the power of money overwhelms the formal political institutions of a democratic society.