Well, "-kun" normally stands for " Mr ". They refer to boys in that way, like " Li-kun ", so it's for the men. " -chan " it's a suffix あなた use for someone close to you, like your best friend, または your pet, etc. But あなた use it only when あなた call them によって their first name. Note: Boys' will be the same, "-kun". "-san" is for someone あなた think is higher than you, like the way Sakura calls Yukito " Yukito-san". Mainly, it's to 表示する あなた have respect for that person. "-sama" is for someone that is of royalty, または あなた respect till the ends of the earth. There's still many, like "-senpai" , "-ou". But I'm not too sure. But when あなた call a person without the suffix, that's means you're VERY close to him/her, like the way Shaoran calls Sakura with out the suffix when he uses her first name.
Okay! I think that's it. Forgive me if I'm wrong anywhere, I'm still a kid and not too bright. lol. Matte ne!
-kun is used for boys. Example: Nina called Mitsuko's name によって "Mitsuko-kun!" when she was excited. -chan is mostly used for girls. But for little boys too! Also for pets. It mostly stands for childish cuteness. Example: Mitsuko 発言しました "Nina-chan", when he showed her Amy. -san is like in a polite situation. Example: Mitsuko 発言しました Nina-san when he greeted her によって saying, "Hello, Nina-san." -sama means in a much もっと見る polite situation. Example: Mitsuko 発言しました "Nina-sama" when he needed her help. Ask me for more, later on.