Susan Miller

USA TODAY

A coalition of more than 100 media organizations on Sunday published what it said was an extensive probe into the offshore financial deals of the rich and famous from documents from a Panamanian law firm, Mossack Fonseca, fed from an anonymous source.

Here's what you need to know

1. What this is: The cache exposes assets of everyone from political officials to billionaires to celebrities to sports stars that were previously undisclosed. The documents expose holdings of 12 current and former world leaders and details of the hidden financial dealings of 128 more politicians and public officials worldwide. Included: At least 33 people and companies blacklisted by the U.S. government because of links to wrongdoing, such as doing business with Mexican drug lords, terrorist groups or rogue nations such as North Korea and Iran. According to Sueddeutsche Zeitung, the Munich-based newspaper that obtained the trove of documents more than a year ago from an anonymous source tied to Mossack Fonseca, the "Panama Papers" include approximately 11.5 million documents — more than the combined total of the Wikileaks Cablegate, Offshore Leaks, Lux Leaks and Swiss Leaks.

Massive leak reveals money rings of global leaders

2. Why should you care: The leak of documents shows how the rich and famous can exploit offshore tax shelters and reveals an unprecedented pattern of corruption worldwide for 40 years, including maneuvers by major banks who created the hard-to-trace companies. World leaders or associates who have embraced anti-corruption platforms are featured throughout. The papers also allege a billion-dollar money laundering ring run by a Russian bank tied to associates of Russian President Vladimir Putin.

Worldwide, jaws drop to 'Panama Papers' leak

3. What shell companies are: A shell company is one used as a vehicle for various financial transactions without having significant assets or operations. It could also be one kept dormant for future use. Shell companies are not illegal. Businesses put assets in offshore structures for various reasons, such as to circumvent currency restrictions. Other people use them in estate planning. However, they are often used as tax havens or to commit fraud, such as creating an "empty" shell corporation with a name similar to a real one, then running up the price of the empty shell and selling it. A video produced by McClatchy, the U.S. partner in the reporting, explains shell companies:

Offshore corporations: The secret shell game

4. What Mossack Fonseca is: Mossack Fonseca is a law firm based in Panama with more than 40 offices worldwide. It specializes in commercial law, trust services, investor advisory and international structures. It operates in tax haven countries such as Switzerland and the British Virgin Islands. Mossack Fonseca denied all accusations of illegal activity.

5. What the fallout could be: Laws vary by country, and it remains to be seen whether any international conventions were violated or the money could be seized. But the political fallout has already begun. Iceland's prime minister, Sigmundur Gunnlaugsson, one of several major politicians named in the documents with alleged links to the shell companies, was expected to face calls for a snap election, Britain's Guardian reported.