Discrimination is the act of making distinctions between human beings based on the groups, classes, or other categories to which they are perceived to belong. People may discriminate on the basis of age, caste, criminal record, height, weight, physical appearance, disability, family status, gender identity, gender expression, generation, genetic characteristics, marital status, nationality,Profession, color, race and ethnicity, religion, sex and sex characteristics, sexual orientation, political ideology, social class, personality, species, as well as other categories. Discrimination occurs when individuals or groups are treated "in a way which is worse than the way people are usually treated," based on their actual or perceived membership in certain groups or social categories. It involves the group's initial reaction or interaction going on to influence the individual's actual behavior towards the group's leader or the group, restricting members of one group from opportunities or privileges that are available to members of another group, leading to the exclusion of the individual or entities based on illogical or irrational decision making.
Discriminatory traditions, policies, ideas, practices and laws exist in many countries and institutions in all parts of the world, including territories where discrimination is generally looked down upon. In some places, attempts such as quotas have been used to benefit those who are believed to be current or past victims of discrimination. These attempts have often been met with controversy, and have sometimes been called reverse discrimination.