Explainer: What Trump is being charged for

Donald Trump is being charged over hush money payments made to a porn star just before the 2016 presidential election.

Following an investigation into the $130,000 payment made to Stormy Daniels in an attempt to keep her silent about an alleged affair, a grand jury has indicted him, reports the BBC.

He is expected to appear before the court in New York on Tuesday, where the charges in the indictment will be read to him.

The indictment makes him the first current or former president of the US to face criminal charges.

One former president - Ulysses S Grant - did get arrested for speeding in his horse-drawn carriage in 1872, but he avoided being charged. Ulysses S Grant had recently led the Union forces to victory in the Civil War.

The Stormy Daniels and Trump story got out when in 2016 the former offered to sell her account of an adulterous affair she had with him in 2006.

Trump's lawyer Michael Cohen paid $130,000 to Stormy Daniels when his team found it out.

Trump's reimbursement to his lawyer for the payment to Daniels was recorded as legal fees, which prosecutors argue amounts to falsifying business records, a misdemeanour criminal offence in New York.

Prosecutors could also potentially allege that Trump's attempt to conceal his payments to Daniels violated election laws, as it was motivated by a desire to prevent voters from learning about his affair with her.

Furthermore, falsifying records to conceal a crime would constitute a felony, which is a more severe charge, but whether or not Trump is guilty of this or a misdemeanour is a matter of debate, with no clear-cut answer.

However, US law does not prohibit a candidate, even if found guilty of a crime, from running for or serving as president, including while in prison.