A stereotype is a belief/bias built either through experience or influence about a class of people which may be true for some but not all people belonging to that class. This generalization of the characteristics causes people to change their attitude towards the members of a group based solely on their membership. Such prejudice can be both positive or negative. If negative, it leads to discrimination in various ways.
Stereotypes arise due to preconceived judgements about people due to their race/ethnicity, gender, social class, age, disability, religion, sexuality, nationality or other personal characteristics