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Each THAAD system is comprised of five major components: interceptors, launchers, a radar, a fire control unit and support equipment, according to Lockheed Martin, the security and aerospace company that serves as the prime contractor for the equipment.
Here's how it works, Lockheed Martin says.
The radar first detects an incoming missile. Those manning the system identify the threat. Then, a launcher mounted to a truck fires a projectile, which Lockheed Martin calls an "interceptor," at the ballistic missile in the hopes of destroying it using kinetic energy -- basically just its sheer speed.
Because it has no warheads on its missiles, instead destroying other projectiles by colliding with them, THAAD is "potentially safer, especially for dealing with nuclear missiles," said Yvonne Chiu, an expert on military policy and diplomacy at Hong Kong University.
"If you hit a nuclear ballistic missile with a missile with no warhead, it would hopefully not cause a nuclear explosion."
Unlike North Korea's mostly untested ballistic missiles program, THAAD has been in use for several years by the U.S. military to protect units in places such as Guam and Hawaii from potential attack.
"North Korea continues to develop their nuclear weapons and ballistic missile programs, and it is the responsibility of our Alliance to maintain a strong defense against those threats," Gen. Curtis M. Scaparrotti, Combined Forces Command, U.S. Forces Korea commander said last month.
"THAAD can add an important capability in a layered and effective missile defense."
Why is it controversial?
While the U.S. maintains that any deployment of THAAD in South Korea would be solely to protect its forces there and their South Korean allies, some see it as further militarization of the peninsula and an escalation of the American presence there.
China especially, tends to view any increase in U.S. military presence in Asia as an attempt to contain it and reduce the effectiveness of its weapons.
Speaking at an event hosted by the Center for International and Strategic Studies think tank in February, Chinese Foreign Minister Wang Yi said the deployment of the anti-missile system could jeopardize "China's legitimate national security interests."
"THAAD has a range that could hit weapons in China," said HKU's Chiu.
While she added that the significance of THAAD deployment in Korea would be more geopolitical than military, Chiu said that China was understandably concerned "about having a U.S. made, U.S. run missile system in its backyard."
"Whenever you add something new, it automatically causes concerns."
"THAAD Is a purely defensive weapon, it is purely capable of shooting down a ballistic missile it intercepts and it is there for the protection of the United States," Secretary of State John Kerry said last month during a visit to Beijing.
"Russia and China have obviously expressed concerns about THAAD," he said.
"We have made it very clear we are not hungry or anxious or looking for an opportunity to deploy THAAD.
"If we can get to denuclearization, there's no need to deploy THAAD."
CNN's K.J. Kwon in Seoul and Shen Lu in Beijing contributed reporting.