"Racism" is simple. It is the assumption by the racist that a person's character, behaviour, abilities and (or in every case) intelligence are dictated by the group to which they belong, as perceived by the racist.

Virtually everybody is racist to some degree, about some groups of people. It helps to be aware of this, and reflect on it, and remember the problem is not how you see it, but how they see it. To them, you are the problem. Much of the time it's pretty harmless- negative reactions to Brummies, Scousers, Norvern Mankies, Kerrymen etc. seldom spill over into genocide. Other times it's hydrogen bomb dangerous- US slavery, South African apartheid, I'm sure you can think of examples yourself.

Sorry to preach. Mild, friendly racism can be good fun, there was an Englishman, a Yorkshireman and a human. But the BBC retransmitted Enoch Powell's infamous speech recently (bumsuckers) and racism is a dangerous joke just now.