Speciesism is the notional act of assigning different values or rights to beings on the basis of their biological species, by analogy with such terms as sexism and racism. The term is used and considered meaningful chiefly by advocates of extensive animal rights -- that is, those who believe that speciesism, so defined, is ethically incorrect and its consequences morally wrong.
Like other words of political and moral disputation (such as the Marxist use of "exploitation", or the various meanings of "sexual liberation"), use of the term implies a certain position on the subject it discusses. To refer to speciesism implies that it is possible and desirable to treat members of various species -- specifically, nonhuman animals traditionally considered "lower" animals -- with moral value equal to that which society bestows upon humans.
In practice the term is used to refer to discrimination against non-human animals by human beings -- that is, to anthropomorphic speciesism. Speciesism is condemned by proponents of what is generally known as animal rights including philosophers such as Tom Regan and Peter Singer. The former rejects it as allowing for unjustified violations of animals' inherent rights; the latter, as being against the principle of equal consideration of interests.
The teachings of some religions can be considered less speciesist than others. For example, while some animists may believe in the equality of sentience of all things, some monotheists may believe that humans are superior by divine intention and inherently a class apart from other lifeforms.
Generally speaking, the teachings of Jainism, Hinduism, and Buddhism are examples of religions which tilt towards being less specieist on a spectrum of various religious beliefs, though the extent to which this is reflected in daily life in countries where those religions are influential is mixed.
See also discussion under physicalism