In its simplest terms, ableism is the categorization and valuation of a bodymind, behavior, characteristic, or community as inferior or superior, unworthy or worthy, useless or useful, normative or deviant. In the united states context, these valuations are in/formed through the application of white supremacist, settler-colonial, cis-heteropatriarchal, capitalist ideas about race, ethnicity, dis/ability, gender, re/productivity, criminality, civility, intelligence, fitness, beauty, birth/living place, etc. In other words, our identities and our purported values are both a function and byproduct of ableism.
Talila A. Lewis, "Understanding Disability, Ableism, and Incarceration More Expansively" from We Are Each Other's Liberation: Black and Asian Feminist Solidarities (edited by Rachel Kuo, Jaimee A. Swift, and TD Tso)