Doberman has written
All Germans are Nazis.
All Americans are fat
All Irish people are drunks
All blacks are stupid.
All Somalians are pirates. ( aar, matey!
)
Etc.
( please don't take offence to that, was just an addition of examples. )
Stereotyping is a normal part of life, and generally it does describe the group of people, eg saying nerds are weak. This makes sense and is usually true, right? However, stereotyping according to race is what is bad about it, saying that fat people can't run is a stereotype, but it is usually true and isn't meant in an insulting way, it's just denoting a group of people. ( when have you ever seen someone really fat being able to complete a 400m sprint? Please, I need to see that YouTube video! )
Do you get what I mean?