The US has just abstained — for the first time ever — on a United Nations vote condemning the US embargo on Cuba, which passed by a whopping 191-to-0 margin, with two abstaining. Every time the measure had come up before, the US voted against it, leaving Washington at odds with nearly 200 other world governments.

Wait. Huh? Who is doing what to whom about what now?

Okay, yes, this is all really confusing. But it’s kind of a big deal. Here’s what’s going on.

1) The US has had an embargo on Cuba since 1962

In February 1962, President John F. Kennedy placed an embargo on trade between the United States and Cuba, in response to Fidel Castro’s provocative policies at home and abroad.

After Castro’s communist revolutionaries seized power in 1959, they began to implement economic policies that directly hurt the US, such as nationalizing all US-owned businesses without compensation and raising taxes on US imports. They also started developing much closer ties to the Soviet Union, the United States’ primary adversary in the Cold War.

In response, the US government, under then-President Dwight D. Eisenhower, broke off diplomatic relations with Havana in 1960, banned nearly all trade between the two countries, and seized Cuban assets in the US. In February 1962, President Kennedy expanded that into a complete economic embargo and put in place strict travel restrictions to and from the country.

The embargo, which requires congressional approval to be rescinded, remains in place to this day.

2) The UN doesn’t like this, and has voted to condemn the embargo for 24 years in a row

Since 1992, the UN General Assembly has voted to approve a resolution condemning the embargo and calling for the US to “take the steps necessary to repeal or invalidate [it] as soon as possible.” Cuban Foreign Minister Felipe Pérez Roque has called the embargo part of a “ruthless, half-century economic war” against his country.

Tomorrow, October 26, the UN General Assembly vote on resolution against the blockade #Cuba #YoVotoVsBloqueo pic.twitter.com/4qOSKjjhXa — Misión Cuba Ginebra (@MisionCubaONUG) October 25, 2016

The reasons the UN objects to the embargo are its adverse effects on the Cuban people (the Cuban government estimates that the embargo has caused around $121 billion in damage to its economy) and the fact that it violates the principle of freedom of international trade and navigation, which all UN member states are obligated to respect.

All of these resolutions, though — including the one that passed today, 191 to 0 — are nonbinding and unenforceable. That means the US doesn’t have to do anything just because the UN passes them. But they do carry some political weight. When nearly 200 UN member countries condemn you for something, it looks pretty bad — especially when you’re claiming to be a beacon of democracy and freedom in the world.

3) The US always votes against the measure — always

Since 1992, the US and Israel have consistently voted against the resolution. When it first passed in 1992, it received 59 yes votes and three votes against, and 71 countries abstained.

These days, pretty much everybody votes for it. In 2015, for example, the resolution was adopted by the 193-member General Assembly with 191 votes in favor. Israel and the United States were the only two that voted no (no one abstained).

4) That is, until the US abstained from today’s vote

Unnamed officials had leaked Washington’s decision to abstain several hours before the vote, so it didn’t come as a particular surprise. Israel, America’s closest ally at the UN, also voted to abstain.

Just to be clear, they didn’t vote for it; they simply refused to cast a vote at all. That saves Washington the embarrassment of voting to condemn itself. Because that would be silly.

That didn’t have any real impact on the vote, which would have passed overwhelmingly even if the US and Israel had voted against it instead of abstaining. But it’s a powerful symbolic gesture designed to signal to the world that the US position on the 55-year-old embargo has fundamentally changed. It’s also something that US Ambassador to the UN Samantha Power was proud to trumpet:

Every yr, @UN votes to end US embargo agnst #Cuba. We've always voted "no." Today, for 1st time ever, we abstained. pic.twitter.com/cbNyy0NRdp — Samantha Power (@AmbassadorPower) October 26, 2016

5) The US is doing this because Obama also thinks the embargo should be lifted — but Republicans in Congress disagree

This decision to abstain instead of voting no on the UN resolution reflects President Obama’s opposition to the embargo. This is part of his broader effort to normalize relations with Cuba.

Starting in 2014, Obama, using his executive authority as president, began relaxing some of the regulations involved in the embargo, including allowing some “authorized travel” to Cuba by Americans, as well as “certain authorized commerce and financial transactions; and the flow of information to, from, and within Cuba.” And last July, the US officially restored diplomatic relations with Cuba.

Those changes are having an immediate effect, particularly on corporate America, which has long been eager to return to what is seen a lucrative tourist market. Tourism and travel companies such as Airbnb, Carnival Cruise Line, JetBlue Airways, and Starwood Hotels have taken advantage of the relaxed restrictions to expand into Cuba, hoping to cash in on what they expect will eventually become a booming new tourist hot spot.

But this policy puts President Obama at direct odds with congressional Republicans, who overwhelmingly support the Cuba embargo. They also object to Obama using his executive authority to relax the embargo’s restrictions, as they see this as Obama essentially abusing his executive power to get around Congress.

7) But this new open policy toward Cuba could be reversed if Trump wins in November

Donald Trump has threatened to reverse the restoration of diplomatic relations with Cuba. Though he had previously stated that he thinks “[t]he concept of opening with Cuba is fine,” at a more recent speech in Miami on September 16, he stated that "all of the concessions that Barack Obama has granted the Castro regime were done with executive order, which means the next president can reverse them. And that is what I will do unless the Castro regime meets our demands."

"Those demands will include religious and political freedom for the Cuban people and the freeing of political prisoners," Trump said.

Hillary Clinton, on the other hand, has publicly called for lifting the Cuba embargo entirely. If she wins the White House and Democrats retake the Senate, it’s even possible to envision lawmakers formally ending the embargo at some point during her presidency.

So while today’s decision to abstain on the UN vote was a major signal to the world that the US is changing its stance on the Cuba embargo, it’s possible that could all be reversed by the time they vote on this resolution next year.