So you have this friend. You want to turn things from a platonic relationship into a romantic one, but they don't want the same thing. They tell you that they just want to be friends. Oh no! You've been "friend-zoned!"
But what does it really mean to be friend-zoned? It means that one person doesn't have romantic feelings for the other and just wants to stay friends but the other wants to date or hookup. The decision is usually unfavorable for the latter and people tend to make a mockery of the "friend-zoned" individual.
People will laugh or feel the "pain" that that person feels and try to cheer them up or even make them feel worse about it by laughing about it.
Now, don't assume that only girls do this to guys just because that's what you're used to seeing in movies and memes. It can happen from anyone to anyone else, and more often than not, it's probably for the best. It is possible that the other person also has feelings for you, but they don't want to ruin the friendship you already have by dating, realizing that things could end badly and that the two of you wouldn't be in each other's lives at all anymore.
This is a possibility that I feel like most people ignore. Believe it or not, that person might not want to date you because having you in their life at all is more important to them than anything. Sure, dating your best friend could end well, but it often ends poorly.
If this ever happens to you, don't push it. Don't get aggressive with the other person. Hopefully, they'll let you ask why in a calm, respectful manner if you're having a hard time accepting it, but otherwise, just accept it.
Take the decision with a grain of salt and realize they don't want to lose you as a friend by potentially messing up a relationship with you. And that should be more important than anything.