Short answers, pulled from the story.
A stereotype is a generalized belief about a particular category of people, an expectation a person holds about every member of a group. The expectation can concern the group's personality, preferences, appearance, or ability.
Explicit stereotypes are conscious beliefs a person knowingly uses to judge others. Implicit stereotypes lie in the subconscious as automatic, involuntary associations between a social group and an attribute, such as linking the electrician profession more often with men even while believing both sexes are equally capable.
In the tripartite view of intergroup attitudes, the stereotype is the cognitive component, the belief, and often occurs without conscious awareness. Prejudice is the affective or emotional component, and discrimination is the behavioral component, the action taken.
Research on stereotype accuracy has yielded mixed results. Studies on national-origin and astrological-sign stereotypes found them inaccurate, while studies on gender stereotypes found them more likely to reflect reality. A 2015 study by Jussim and colleagues argued some aspects of ethnic and gender stereotypes are accurate while those concerning political affiliation and nationality are much less so.
Stereotype threat occurs when people are aware of a negative stereotype about their social group and feel anxiety that they might confirm it. Claude M. Steele and Joshua Aronson first showed it can depress intellectual performance, with black college students scoring worse than white students on a verbal test framed as a measure of intelligence.
The term was first used in the printing trade in 1798 by Firmin Didot to describe a printing plate that duplicated any typography. It was not used in the modern psychological sense until 1922, when American journalist Walter Lippmann used it in his work Public Opinion.
Stereotypes can form through correspondence bias, the tendency to attribute behavior to personality while underestimating situational factors, and through illusory correlation, an erroneous inference linking two infrequent events. David Hamilton and Richard Gifford demonstrated the illusory correlation effect in a landmark 1976 study.