Anti-racism includes the actions, policies, and theories that challenge and oppose discrimination, inequality, and prejudice based on race.
Oppression is the use of power to disempower, marginalize, silence or otherwise subordinate one social group or category, often in order to further empower and/or privilege the oppressor. Social oppression may not require formally established organizational support to achieve its desired effect; it may be applied on a more informal, yet more focused, individual basis.
An ally is "an individual who actively and continuously strives towards promoting justice and ending marginalization." (College of Dupage Library, "Anti-Racism and Anti-Oppression: Allyship")