Criteria for ratings:
S (General audiences): Violence: Mild (many cartoons, many Charlie Chaplin films)
S (General audiences): Sex: Mild sexual references, nudity (even full frontal) (In the Mood for Love, Tin Cup)
K-7: Violence: Mild violence (Princess Mononoke, The Mask of Zorro)
K-7: Sex: Not much diffecence to S rating (Just Married)
K-11: Violence: Many action comedies, adventure films, close to pg-13 (The Day After Tomorrow, Hellboy)
K-11: Sex: Soft erotic(The End of the Affair, 2046, American Pie (US unrated version))
K-15:Violence: Lots of violence, but not too explicit. Most action and war movies. (Goodfellas, The Terminator, Bad Taste (because of humour))
K-15: Sex: Pretty much everything that's not hard core. (Dreamers, Monsters Ball (both US unrated versions))
K-18:Violence: Extreme violence (Ichi the Killer, Kill Bill Vol. 1, Braindead)
K-18: Sex: Hard core (Ken Park, Caligula)
KK(Banned): Earlier we had tight censorship and films like The Texas Chainchaw Massacre got banned. Today no normal movies get banned (I don't know a single movie that would get banned today). Only stuff that is illegal (for exaple real violence as an entertainment (stuff like jackass (K-15) doesn't count). I can't come up with any example) The law is about the same as the law in US.
If you are 2 years or less younger that the rating you need to have a full age guarding with you. Otherwise you won't get in. K-18 is an exception, only those who are 18 or older can get in.
No restriction for selling movies (except KK). Movies are never cut (by us) for lower rating.