Do young kids understand playful teasing the same way adults do?

I have a 4-year-old niece and sometimes I joke around with her in a silly way. Obviously I’m not trying to be mean, more like playful family teasing.

But then I started wondering if kids that young actually understand the joke, or if they might feel bad even when adults think it’s harmless.

Where’s the line between being playful and accidentally hurting a kid’s feelings?