Cultural appropriation is basically when someone essentially steals the culture of another while taking credit for the originality. You will most commonly find this in white celebrities who have paid thousands of dollars desperately buying physical features minorities were born with. The most famous cultural appropriator was Elvis Presley who went to the hood and learned how to move and sing like a black man then profited off of it as if it was his own unique, original trademark.
I think @xhoneyxbeex post about the indian headdress in fashion is a perfect example of cultural appropriation and to a degree Kylie Jenner new hairstyle. Was it something she wanted or something intended to provoke a reaction.
Cultural appropriation is someone "stealing" the culture of another while taking credit for the originality. So excuse me if I offend anyone, but white girls joining a natural hair movement for black girls. Or the Kardashians taking other cultures and posting it up, sometimes using it the wrong way or doing it because they like it without any credit.
I've mostly seen it as pretending to be apart of another culture or disrespecting a culture. For example, there's tons of videos on YouTube about "how to look Korean/Japanese" etc which is disrespectful because it's fetishizing and claiming that everyone from those cultures look or act a certain way. Just think if there were videos on YouTube called " how to look or act black/white" people would probably be furious at that point. What is also common is people who claim to be 100% Native American (I'm talking about full white or black peoples here) which can be seen as culture appropiation as well.