What do the suffixes -kun, -chan, -san and -sama mean?

They are Japanese honorifics. They are used like suffix (they are added to the end of a name) to show respect.

Kun is mostly used toward young men/boys.

Chan is considered to be very feminine. It is used among close female 프렌즈 또는 family, for the most part.

San is the most common and it's used with guys and gals.

Sama is the formal version of san. It is used when speaking to someone older than 당신 또는 someone in a higher rank.

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 당신 use for someone close to you, like your best friend, 또는 your pet, etc. But 당신 use it only when 당신 call them 의해 their first name. Note: Boys' will be the same, "-kun".
"-san" is for someone 당신 think is higher than you, like the way Sakura calls Yukito " Yukito-san". Mainly, it's to show 당신 have respect for that person.
"-sama" is for someone that is of royalty, 또는 당신 respect till the ends of the earth.
There's still many, like "-senpai" , "-ou". But I'm not too sure. But when 당신 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!

Actually san is mostly used for addressing a stranger and sama is right but also used for master

-kun is used for boys. Example: Nina called Mitsuko's name 의해 "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 said "Nina-chan", when he showed her Amy. -san is like in a polite situation. Example: Mitsuko said Nina-san when he greeted her 의해 saying, "Hello, Nina-san." -sama means in a much 더 많이 polite situation. Example: Mitsuko said "Nina-sama" when he needed her help. Ask me for more, later on.

-kun is used for someone close to u and it's used for boys (i think)

-chan is used for girls and cute stuff

-san is 더 많이 formal

-sama is used for someone who is higher ranks than u

-senpai is for someone a little older 또는 a grade/year higher than u