What is a widely held but fixed and oversimplified idea of a particular type of person or thing called?

Richie, I think you’re confusing stereotype with typecast.

I'm not a Stef person

Tremain White, Sometimes knewledge becomes a burden and to offset the weight one quickly experiences ignorance, stereotypes. careful. ! ! !

Going to listen to the Specials now brilliant track.

In personal terms, the mistaken oversimplification of the particular - by recourse - only to the general = stereotype.