What qualifies as "cultural appropriation"?

How would you define it?

What is the difference between cultural appropriation and plain old disrespect? Do the intentions matter?

Is it cultural appropriation when a white person has dread locks? When a white person runs a food truck that sells Mexican food?

Can a minority appropriate another minority’s culture or does it always have to involve the majority?

Does cultural appropriation clash with the concept of a multicultural society? Seems like a tall order to expect cultures to live together but not borrow from each other.

I’m asking all these questions because I genuinely find the concept of “cultural appropriation” confusing. If someone who understands it better can explain it, that would be great.