President Trump announced pardons for 15 people on December 22 night. The recipients included former congressmen who had pleaded guilty to corruption and military contractors convicted of taking part in a massacre in Iraq. And on December 23, Trump announced a new batch of pardons, including ones for friends and loyalists.

Trump is widely expected to grant more pardons during his remaining 27 days in office, and these could include some very high-profile people such as former spy Edward Snowden or Trump's children.

All of this raises questions about how Presidents hand out pardons in the first place, how you obtain one, and how Trump's use of the power compares to other Presidents. Here is a plain English Q&A about the process:

Have all Presidents given out pardons?

Yes, the power is set out in the U.S. Constitution and is derived from the ancient right of English kings to issue clemency. Every President has used the pardon power. That includes George Washington, who issued the first U.S. pardons, to farmers who led an insurrection called the Whiskey Rebellion.

What exactly is a presidential pardon?

A pardon from the President means you're forgiven for federal crimes you have committed or may have committed. The pardon doesn't wipe out the record of the conviction, but it does eliminate any consequences that go with it—such as limits on voting or buying a gun.

The President can also issue commutations, which can reduce a prison sentence or cut it altogether. But commutations don't wipe out the other consequences that go with a conviction.

It's also important to note the President can't pardon people for state crimes. This could be significant given that states like New York are reportedly conducting investigations into potentially illegal activity by Trump and his family.

How do you get a presidential pardon?

You ask for one. Traditionally, this means applying through a process overseen by the Department of Justice. But as law professor Randall Eliason notes in this excellent overview, President Trump has mostly ignored that formal process and just issued pardons based on his own whims.

How do Trump’s pardons compare to those issued by earlier Presidents?

So far, Trump stands out for how little he has exercised his clemency power—fewer than 100 times so far, and he is on pace to issue the lowest number of pardons or commutations since President McKinley at the turn of the 20th century. In contrast, this Pew study notes President Obama granted 212 pardons and 1,715 commutations, though that was over an eight-year period.

Trump's clemency activity also stands out in that most of it has been in service of political cronies and those with whom he has a personal relationship. Past Presidents have mostly—though not entirely—used the pardon power to address systemic injustice, such as racist drug sentences, or to address broader political riffs in the country, such as President Carter's decision to forgive those who left the U.S. to avoid military service in Vietnam.

Of course, Trump has plenty of time left to exercise his pardon power, so a true comparison will have to wait till he leaves office.

What are some of the most famous presidential pardons?

The most famous pardon came from President Ford, who issued a broad pardon to his predecessor, President Nixon. (Some note that Trump could resign in order to have Vice President Pence step into his role and do the same thing.)

Other noteworthy pardons include President Clinton's decision to issue one to fugitive banker and political ally Mark Rich, and President Reagan's decision to forgive New York Yankees owner George Steinbrenner for illegal political contributions. More recently, President Obama's most famous act of clemency was to commute the sentence of Chelsea Manning, who leaked military secrets. USA Today has a list of these and other famous pardons.

This story has been updated to note the pardons announced on December 23.