Are kindness and niceness the same?

I see stickers, signs, memes, and t-shirts everywhere that say, "Be Kind." Sometimes, the messages go further and intone that there isn't a cost for being kind--"Be kind, it's free." As I have pondered what it means to be kind, I have decided that not everyone shares the same understanding or definition of kindness. I would even challenge, that many people have kindness and niceness confused or that they have conflated the two into one definition. While kindness and niceness can appear to be the same action or character trait, I believe they are not synonymous, interchangeable terms.

What does kindness mean to you?