Activism consists of efforts to promote, impede, direct, or intervene in social, political, economic, or environmental reform with the desire to make changes in society toward a perceived greater good. Forms of activism range from mandate building in the community (including writing letters to newspapers), petitioning elected officials, running or contributing to a political campaign, preferential patronage (or boycott) of businesses, and demonstrative forms of activism like rallies, street marches, strikes, sit-ins, or hunger strikes.

Activism may be performed on a day-to-day basis in a wide variety of ways, including through the creation of art (artivism), computer hacking (hacktivism), or simply in how one chooses to spend their money (economic activism). For example, the refusal to buy clothes or other merchandise from a company as a protest against the exploitation of workers by that company could be considered an expression of activism. However, the most highly visible and impactful activism often comes in the form of collective action, in which numerous individuals coordinate an act of protest together in order to make a bigger impact. Collective action that is purposeful, organized, and sustained over a period of time becomes known as a social movement.

Historically, activists have used literature, including pamphlets, tracts, and books to disseminate or propagate their messages and attempt to persuade their readers of the justice of their cause. Research has now begun to explore how contemporary activist groups use social media to facilitate civic engagement and collective action combining politics with technology.