The United States is hopeful talks between Kim and Moon will make progress on achieving peace and prosperity, the White House said in a statement as the two men began their summit.
All of this is being used to update the US government's classified file on Kim's behavior, motives, personality and leadership style to help Trump and his aides develop a strategy for dealing with Kim at the expected first-ever meeting of USA and North Korean leaders.
Seoul says North Korean leader Kim Jong Un and South Korean President Moon-Jae-in will plant a tree together and inspect an honor guard after Kim walks across the border for the leaders' historic summit.
Critics say Kim may see the summit as a way to burnish his worldwide standing and legitimize North Korea's declared status as a nuclear power. "(T) he Vatican supports and encourages all useful and earnest endeavours to build a better future through meetings and friendship".
In the past, North Korean support for "denuclearisation" of the Korean peninsula has been code for the removal of USA troops from the South and the end of its nuclear umbrella over its security ally - prospects unthinkable in Washington.
Three Americans remain in captivity in North Korea and Trump has said his administration is working to secure their release.
North Korea may also be looking to use whatever happens in the talks with Moon to set up the Trump summit, which it may see as a way to legitimize its declared status as a nuclear power.
The right moves by Kim and wrong ones by Trump could therefore leave North Korea as a happy-faced threat to humanity, prompting nuclear proliferation through neighbours starting their own programmes or sales across the seas to such eager connivers as Iran.
The two will be escorted by South Korean honour guards to an official welcoming ceremony before beginning official dialogue at 10:30am at Peace House, a South Korean building inside the border truce village of Panmunjom. September 3: North Korea conducts its sixth and most powerful nuclear test, which it says was a detonation of a thermonuclear warhead designed for ICBMs.
South Korea has repeatedly hinted that Kim is willing to go for a complete, verifiable and irreversible denuclearization, or CVID.
The Koreas held their second summit in October 2007 between Kim Jong Il and Roh Moo-hyun, Kim Dae-jung's liberal successor and the political mentor of current South Korean President Moon.
After they sign an agreement a joint statement will be issued.
But the mostly likely outcome is something in between, perhaps an agreement to keep discussing a freeze on North Korean nuclear development.
"I feel North Korea is sending their key military officials to the summit as they too, believe denuclearisation and peace are important", he said.
Trump revealed more information about outgoing CIA Director Mike Pompeo's secret trip to North Korea this month, saying Pompeo wasn't supposed to meet with Kim, but that they ended up talking for more than an hour.
He additionally advised reporters that he has a "quite simple" view of North Korean denuclearization: "It means they eliminate their nukes".
By agreeing to meet Kim, Trump has shown his confidence in his reputed deal-making capacity.