In a never-before-seen video posted by the MSNBC host Chris Hayes, Bill Gates says President Donald Trump twice asked him the difference between HIV and HPV.

Gates met with Trump in March 2017 and again in March of this year.

HPV is a very common sexually transmitted disease that causes no symptoms in many people. HIV is a virus that can lead to the onset of AIDS, a condition that is often deadly if left untreated.

In a video posted by MSNBC on Thursday, Microsoft cofounder Bill Gates says President Donald Trump twice asked him the difference between HIV and HPV.

"He wanted to know if there was a difference between HIV and HPV, so I was able to explain that those are rarely confused with each other," Gates tells an audience in the video.

Watch for yourself:

—All In w/Chris Hayes (@allinwithchris) May 17, 2018

For the record: HPV, or human papillomavirus, is a very common sexually transmitted disease that often causes no symptoms but is linked to an increased risk of cancer in some people. HIV, the human immunodeficiency virus, is a sexually transmitted virus that depresses the immune system and can lead to the onset of acquired immune deficiency syndrome, or AIDS, a condition that caused 1 million deaths in 2016, according to the United Nations.

It's not clear where or when Gates was speaking when the video was taken, though a tweet from the MSNBC host Chris Hayes, whose program, "All In With Chris Hayes," shared the footage, gives us a clue: "Bill Gates says that in *both* meetings he had with Trump, Trump asked if HPV and HIV were the same thing," Hayes tweeted.

Gates, a critic of Trump's policies, has met twice with the president, once in March 2017 and again in March of this year, suggesting the video was recorded in the past few months.

This wasn't Gates' only time speaking publicly about the content of his meetings with Trump. In April, Gates said Trump offered him a role as White House science adviser, which he declined, saying it was "not a good use of my time."

The Bill and Melinda Gates Foundation, where Gates spends most of his time, has made tackling the spread of HIV and AIDS a core cause.

"All In With Chris Hayes" also published a longer video of Gates' remarks:

—All In w/Chris Hayes (@allinwithchris) May 18, 2018

The White House did not immediately respond to a request for comment. Representatives for Gates did not immediately respond to a request for comment.