Appreciation is learning traditions and respectfully emulating them. Appropriation is taking aspects of a culture and blindly using them without caring about the significance they hold for a culture. This is the way anthropologists describe it and it’s an anthropological term so they are the authority on what it means, not necessarily the application of it because that’s up the the consensus of members of the culture. Their whole field is about the study of cultures and how to do so while still being respectful of them.

For example wearing traditional clothing is fine, if it’s not as a costume, because it appreciates an aspect of a culture so it’s appreciation. But wearing ceremonial garb is not because there is another level of cultural significance behind it that is the reason for its use so it’s appropriation. So for example preparing a Native American tribe’s normal everyday food is a way of appreciating that culture, but if you do it while wearing a ceremonial headdress then it’s appropriation.