From National Museum of African American History and Culture:

Race does not biologically exist, yet how we identify with race is so powerful, it influences our experiences and shapes our lives. In a society that privileges white people and whiteness, racist ideas are considered normal throughout our media, culture, social systems, and institutions. Historically, racist views justified the unfair treatment and oppression of people of color (including enslavement, segregation, internment, etc.). We can be led to believe that racism is only about individual mindsets and actions, yet racist policies also contribute to our polarization. While individual choices are damaging, racist ideas in policy have a wide-spread impact by threatening the equity of our systems and the fairness of our institutions. To create an equal society, we must commit to making unbiased choices and being antiracist in all aspects of our lives.

Being antiracist is fighting against racism. Racism takes several forms and works most often in tandem with at least one other form to reinforce racist ideas, behavior, and policy. 

Read the full portal here.