Speciesism is the granting, acknowledging, or withholding of rights and privileges on the basis of species.
Speciesism can be a form of unfair discrimination when the granting or withholding of rights and privileges is based on morally irrelevant criteria. For example, many believe that it is wrong to kill and eat a pet dog or cat, but they think it's perfectly fine to kill and eat a pig, cow, chicken, or fish. There is no morally relevant criteria that would make such a distinction between those species fair. The only basis for this unfair discrimination is speciesism.