Not sure what's going on with North Korea? Here's what you need to know.

North Korea is run by an eccentric dictator who was once thought to have ordered all the men in the country to get his haircut.

He has executed family members and is generally antagonistic towards most foreign powers.

Yesterday Kim Jong-Un claimed that North Korea has successfully detonated a hydrogen nuclear bomb.

The rest of the world isn’t quite sure whether that’s true – but either way things are tense.

Not sure what’s going on? Here’s what you need to know:

1. Did they actually detonate a bomb? 

Something blew up. Whether it was a hydrogen nuclear bomb or not is what no one is sure about just yet.

Watch the announcement of the test on North Korean state TV:

The United States Geological Survey said a 5.1 magnitude earthquake was detected in the region of North Korea where a nuclear bomb was tested in 2013.

The size of the explosion has led to speculation that if it was a nuclear bomb, it might have been an atomic one, not a hydrogen one, which is far more powerful.

Most experts seem to agree that if this was really the kind of test North Korea claims then the reading would have been much higher. Up to 10 times higher, even.

This is the fourth nuclear test by the secretive regime, and we may never know for sure if the bomb was what it is claimed to be.

2. Why is a nuclear North Korea a big deal?

North Korea’s nuclear program has been a long-standing concern for neighbours South Korea and Japan, and for the rest of the world who aren’t that keen to get caught up in another nuclear arms race.

UN Secretary General Ban-Ki Moon says the test is “deeply troubling”.

“The underground nuclear test announced by the Democratic People’s Republic of Korea on 6th January is deeply troubling. It is also a grave contravention of the international norm against nuclear testing,” he said.

3. Why does the kind of nuclear bomb matter?

A hydrogen bomb would signal a nuclear program far more powerful and advanced than anything that North Korea has achieved before.

North Korea claims the hydrogen bomb they tested was “miniaturised”, which if true could lead to powerful nuclear missiles which could travel further than before.

Jean Lee, an expert in North Korean studies from Yonsei University, told ABC radio North Korea’s target was the United States, its “main enemy”.

“They have been developing missiles designed to reach US territory,” she said.

4. So why would North Korea do it?

North Korea is an aggressive, oppressive, isolationist dictatorship with an appalling human rights record and an antagonistic relationship with its nearest neighbours.

Kim Jong-Un is also said to be incredibly paranoid. He wants authority and a way to fend off internal and external threats.

He appears to have turned to nuclear weapons as one solution.

After yesterday’s test, Jong-Un said “Let the world look up to the strong, self-reliant nuclear-armed state” in a handwritten note shown on North Korean State TV.

At the most basic level, having nuclear weapons is essentially North Korea’s insurance policy against perceived threats and attempts to overthrow the regime.

5. Do we still need to be worried?

Just because the size of the explosion indicates it probably wasn’t a full-blown hydrogen bomb, experts say the test is concerning.

James Acton, co-director of the nuclear policy program at the Carnegie Endowment for International Peace said a failed hydrogen bomb test is one possibility of what happened.

“If North Korea felt confident enough to even try it — a true two-stage thermonuclear weapon — if it thought its technology was at that level, that would be disquieting,” Acton told Politico.

“Clearly, it’s better that it failed than succeeded but you can learn stuff from failure if you do the instrumentation correctly,” he said.

“Even if it was a failed hydrogen bomb, that would still be somewhat worrying.”

And no matter what kind of bomb it was, a nuclear test is a provocative act.

“Regardless of the type of weapon, this kind of provocative and dangerous behaviour escalates tensions on the Korean peninsula and proves that North Korea continues to be a threat to regional stability and international peace and security,” Foreign Minister Julie Bishop said.

It may not be possible to ever know for sure what went down yesterday, but what we do know is certainly concerning.