What differentiates that act of simply grouping people from the act of sterotyping?

How can sterotyping effect group relations?

When you group people, you say "These people are Italian." When you stereotype, you make statements such as "Italians are loud."

In other words stereotyping makes assumptions about individual behaviors based upon their group.

The word stereotype refers to a simplified and standardized image held by a group of people. It is based on some kind of knowledge that is usually incorrect. There is basically no difference between grouping people and stereotyping them But Stereotyping usually is based on a specific belief. Whereas grouping can have many different real or virtual reasons.