B.O. said during the first debates that he would reach out to NK, Iran, Syria, et al WITHOUT PRECONDITIONS. That was roundly criticized by both sides.
Trump has accepted an invitation to meet with KJI because they've agreed to nuclear disarmament.
What's also apparently on the table is the legal end to the Korean War (we're still just in a truce of that war), and potentially the reunification of some sort of the entire peninsula.
If you can't see the difference in the two positions of our Presidents former and current, then I don't know what else to tell you.