Korean word order is subject-object-verb: "I-subject him-object see-verb." Subjects, especially, I and you, are often omitted if these are clear from the context.
There are no adjectives but verbs with the meaning of an adjective which an be used as a verb or like an adjective.
There are no articles, genders, or declensions. It has extensive verb conjugations indicating tense and honorific level. There is a plural form, but it is very often omitted.
Korean has postpositions instead of prepositions: hanguk-e, "Korea in" instead of "in Korea."
Koreans refer to each other rather in terms like elder brother, elder sister, younger sibling, uncle, aunt, grandmother, grandfather, manager, teacher etc. than by using the word you. It's not uncommon to refer to yourself by using such an expression. You can also call somebody an aunt, uncle or brother if this person is actually not. Most korean girls call their boyfriend older brother.
Depending on the relation to the person you have conversation with, it's necessary to find the correct level of politeness. If the person is considered to be higher in the hierarchy, a very polite form has to be used, while this person will use a less polite form to address you as a lower person. Koreans often ask very personal questions (about your age, occupation, income, family status etc.) in order to find out in which form they should use when talking to you.