You wouldn't say the second one in practice because of the meaning. used to + verb refers to past habits. You are talking here about what you did at a specific time in the past. Naturally, you could say: "I used to live in Korea. I lived there 2 years ago for several months". "When I lived in Korea, I used to e.g. attend Korean classes, eat Korean food.

Your first example, I lived in Korea, is in the Past Simple tense. This tense is used to talk about something that has finished at some point in the past. Your second example, I used to live in Korea, is used to talk about a habit or something you did on a regular basis in the past but no longer do now.

Hi Kazuma, *I used to live in Korea 2 years ago* We use "used to" to refer to actions that occurred habitually in the past, but do not occur anymore now. It also refers to things that were true but is no longer true. *I lived in Korea 2 years ago.* The use of simple past tense here simply emphasises the fact that Korea was your country of residence at a point in time (two years ago). Just as a side discussion, "used to verb-ing" refers to a habitual action that is still ongoing; as a result, we have become very familiar with the action. Example: John USED TO ANSWER every email that he received, but he is now USED TO IGNORING those that do not really matter. Hope this helps. Cheers, Lance

There isn't a difference at all colloquially between those two sentences, they both mean the same thing though just saying "I lived in Korea 2 years ago." is more casual sounding. Both sentences are in the past-tense thus meaning the same thing.