Cultural appreciation:

example:

I have an interest in X culture for whatever reason so I am going to study their history, their beliefs, customs, language, and other aspects of their culture as long as it is appropriate for me to do so.

Cultural appropriation:

Example: Indians are like free and cool. I am going to wear this warbonnet. It is sacred and only meant to be worn by those who have earned it from very few tribes but whatever I can still wear it.

Basically cultural appropriation is participating in an activity and or taking an aspect of a culture that is not your own, thereby misusing said item or wrongly participating in a stereotyped reenactment of that culture.

Cultural appreciation is learning about a culture, within a respectful boundary.