What does friend-zoned mean?

The "friend zone" is where girls befriend the nice guys while they go after complete s, then complain to their "friend zoned" friend about what happened after they get dumped. 

In other words, the "friend zone" isn't so friendly.

Characters:

Amber liu

Amber is the queenka of Seoul International High School and she's the first ever tomboy to become a queenka. 
Amber isn't afraid to be herself in her school full of saturated cookie cutter, uber-typical girly girls. 
Amber listens in class, but doesn't have the best grades. 
Amber turns every girl into a lesbian just by one look along with her signature smile. 
Amber is a laid back type of girl who only succeeds in sports. 
A perfect mixture of masculine and feminine traits. 

kris wu

Kris, who is a geek that is a tag-along to Amber. 
Amber's first real guy friend she could talk about all her problems with. 
Secretly, the next heir to Wu Corporations. 
Handsome without his glasses that he refuses to take off. 
Also wears polos and checkered shirts that have the buttons all the way to the top. 
Kris is a straight A student who also helps tutors Amber throughout the school year.  
Kris is the tallest within his school. 
A perfect mixture of the boy next door.