@AC14747,
It's actually pretty simple.
Racism is believing that one or more races are inherently inferior to one in particular.
Not wanting to stand next to someone because they are black could meet the definition of racism, but if it's because they are afraid of getting mugged, it's prejudice.
Of course it's not as if prejudice is a virtue while racism is the most heinous of crimes a human could commit (although the Left like to think the latter is true).
Neither is anything to be proud of and is indicative of flaws in a person's character.
But prejudice transcends race and is, in my opinion, a lot more prevalent than racism, again though, it is never a virtue except perhaps in a moment of life and death crisis...but then, only if your prejudice turns to have been accurate.