VIENNA (AP) — Iran and six world powers reached a landmark deal on Tuesday meant to curb Iran’s nuclear program in exchange for sanctions relief. A look at the main points:

From left to right, Chinese Foreign Minister Wang Yi, French Foreign Minister Laurent Fabius, German Foreign Minister Frank Walter Steinmeier, European Union High Representative for Foreign Affairs and Security Policy Federica Mogherini, Iranian Foreign Minister Mohammad Javad Zarif, Head of the Iranian Atomic Energy Organization Ali Akbar Salehi, Russian Foreign Minister Sergey Lavrov, British Foreign Secretary Philip Hammon, U.S. Secretary of State John Kerry and U.S. Secretary of Energy Ernest Moniz pose for a group picture at the United Nations building in Vienna, Austria, Tuesday, July 14, 2015. After 18 days of intense and often fractious negotiation, world powers and Iran struck a landmark deal Tuesday to curb Iran’s nuclear program in exchange for billions of dollars in relief from international sanctions — an agreement designed to avert the threat of a nuclear-armed Iran and another U.S. military intervention in the Muslim world. (Carlos Barria, Pool Photo via AP)

—ENRICHMENT: Iran will reduce the number of uranium-enriching centrifuges it has from almost 20,000 to 6,104, and reduce the number of those in use from some 10,000 to about half that. Those limits will be in place for 10 years, then gradually relaxed over the next three. Iran also commits to using only its current models, rather than more advanced centrifuges it had wanted to install. Centrifuges spin uranium to concentrate it into levels that can range from reactor fuel to the fissile core of a nuclear weapon.

—STOCKPILE: Iran has already rid itself of stockpiled uranium that was enriched to one step from weapons-grade material. It is now committed to reducing its remaining stockpile — less-enriched uranium that is harder to use for nuclear arms — from about five tons to 300 kilograms (less than 700 pounds) for 15 years. U.S. officials say that at this level it would take Iran at least a year to enrich enough uranium for a nuclear weapon.

—UNDERGROUND SITE: Iran committed to convert its Fordo enrichment site — dug deep into a mountainside and thought impervious to air attack — into a research center. The site will still house centrifuges but they will make medical isotopes instead of enriching uranium, and there will be less than a tenth as many of them

FILE – This Jan. 15, 2011 file photo shows the heavy water nuclear facility near Arak. Iran and six world powers reached a landmark nuclear deal on Tuesday, July 14, 2015 meant to place long-term verifiable limits on nuclear programs that Tehran could modify to make atomic arms. All past UN Security Council resolutions on the Iran nuclear issue will be revoked simultaneously with Iran’s compliance with its commitments at Fordo, Arak, its implementation of agreed-on transparency and honoring other responsibilities. U.S. officials said Tuesday all that stands and more an arms embargo and sanctions imposed on Iran’s ballistic missile programs will remain under a new resolution for five to eight years. (AP Photo/ISNA, Hamid Foroutan, File)

as there originally were.

—TRANSPARENCY: Iran will give more access to its nuclear program to the U.N. nuclear agency. If that agency identifies a suspicious site, an arbitration panel with a Western majority will decide whether Iran has to give the agency access within 24 days. All sites, including military ones, may be inspected if the agency has solid evidence of undeclared nuclear activity.

—REACTORS AND REPROCESSING: Iran must redesign its nearly built reactor at Arak so it can’t produce plutonium for nuclear weapons.

—SANCTIONS: All U.S. and European Union nuclear-related sanctions will be suspended after experts have verified that Iran is hewing to its commitments. If at any time Iran fails to fulfill its obligations, those sanctions are supposed to snap back into place. An arms embargo will stand for five years and restrictions on Iran’s ballistic missile programs for eight. Iran will get some access to currently restricted sensitive technologies.