Iran and six Western countries have agreed to a deal limiting Iran's nuclear program and ending severe economic sanctions.

Here are six things you need to know about the deal:

1. Iran can buy and sell again

The U.S. and the European Union have agreed to end a variety of punitive sanctions against Iran. That will mean Iranian oil exports to the West can resume, leading to expectations that world oil prices will remain lower. That's good for world economies in general, but not for oil producers like Canada.

Iran can open bank branches in EU countries and resume trading with the EU. Similarly, U.S. companies will be free to do business with Iranian banks. They can also resume selling passenger aircraft to Iran.

2. No nukes, they promise

In return, Iran agrees to cut its enriched uranium stockpile by 98 per cent and to remove two-thirds of its centrifuges (devices that can enrich uranium to the point it can be used to make nuclear weapons).

3. Peaceful reactor allowed

Iran will be allowed to redesign and rebuild a heavy-water research reactor to be used only for peaceful purposes. Critics have said the country can't be trusted not to cheat. The U.S. says there will be verification checks.

4. Israel thinks it's crazy

Israel has been implacably and unrelentingly opposed to any pact with its Iranian neighbour — and remains so. Prime Minister Benjamin Netanyahu says Israel will itself continue to prevent Iran from developing nuclear weapons. Defence Minister Moshe Yaalon told the New York Times: "Obviously we are going to have to continue to prepare to defend ourselves by ourselves."

The Israelis say ending sanctions will only allow Iran to finance more state-sponsored extremism aimed largely at them. Criticism of the deal crosses political lines, the Times reports, though there are differences about how Israel should respond.

5. Obama can veto opposition

In the United States, Congress has already voted itself a 60-day review period on any nuclear deal with Iran. President Barack Obama must put all concessions on hold until that is over. He said Tuesday, however, that he would veto any attempt by Congress to scupper the agreement.

6. How it all began

The Iran nuclear deal dates back to August 2002, when Western intelligence services and an Iranian opposition group discovered the country was producing enriched uranium at a secret site in the eastern city of Natanz that could lead to material suitable for weapons.

The United Nations imposed the first sanctions against Iran in 2006, banning the sale of sensitive nuclear technology. Five more Security Council resolutions were passed by 2010, tightening the sanctions on Iran.

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Iranian Foreign Minister Mohammad Javad Zarif, left, and British Foreign Secretary Philip Hammond leave the final press conference of Iran nuclear talks at Austria International Centre in Vienna, Austria on Tuesday. (AFP/Getty)

With files from The Associated Press