Activists are people who campaign for social or political change. They do public protest or rally. They serve as the voice for those who can't express their deep concern for the society.
One of the most well-known activists is the LGBT group. LGBT stands for "Lesbian, Gay, Bisexual, Transgender". They call for a change in the way people treat them. They want freedom of expression. They want the society not to arbitrate their means of showing up themselves.
Another one is the women's rights activists. It's a group of women trying to call for equal rights and opportunities for all men and women.
Some other activists are the following:
- animal rights advocates
-civil rights leaders
- environmental organizations
- peace activists
( I bet it's self-explanatory what these activists are trying to reform.)