When we talk about stereotypes as phenomenon, these are beliefs about members of certain group who will act and think in the same fashion. That are labels, and we will recognize every person accord group which she belongs. When we decide to think accord this beliefs, life will be closed box and all impressions will be predictable.
Some of usual stereotypes are:
About young people. They are green and they don't know nothing about life.
About blondes. They are stupid and easy women.
About elders. They forgot all what they know and they are not in steps with time.
About models. They are anorexic, bulimic skinny girls without brain.
About policemen. They have small intelligence. Jokes are often about them.
About footballers. They are also not so smart.
Thinking accord stereotypes could be negative or positive, but in both cases this is superficial perception. Imagine that you walk in the park and group of young men who wear leather jacket is there. You will feel insecure and fear will come in your mind, because they can hurt you, they can be a gang. In the same time, if you see bunch of kids around, you will feel safe, because they can't harm you. The same we can tell about men on motorcycles. We will be afraid to be close if our beliefs belong to stereotypes.
If you see young girl with hard makeup and short skirt in the nightclub, you will think she is easy, even she could be a prostitute. You don't wish to dig more, because otherwise you could see that she is business woman who came to have fun and to relax. Once policemen in USA caught Heather Locklear because she was wearing very short skirt, they did not recognized actress and it was indeed funny. She left impression as she is prostitute. It is not once that some people will be hold at airport, if their face reminds on terrorist. Especially nowadays, grumpy look , black hair and beard could be suspicious.
Also if you see man in business suit, you could think that he is manager. He can be criminal or someone without money, he could borrow or even steal this suit to represent himself as elegant business man. If you live with labels, your impression can be destroyed in the moment when you start to think about other side. Blond girl was maybe easy for you because she slept with you very fast, but she has kids and husband and they are in marriage for a 20 years. Maybe you were victim of stereotypes too, if you are guy with muscles and great body, she could consider you as good opportunity for one night stand.
When some things are important for us, it is recommended that we don't jump with conclusions. Stereotypes are hot sauces, we could burn on our own beliefs. Things are not always as they look like, and also it looks limited if you put all people in one group, without making differences between them. Then you will get label, as person who is small minded and primitive.