Billionaire Bill Gates has told of how he had to school President Donald Trump on the facts of life, explaining that human immuno-deficiency virus and human papilloma virus are not the same thing.

In a video of a Bill and Melinda Gates Foundation event this week obtained by US broadcaster MSNBC, the Microsoft founder spoke to an audience about his odd conversations and encounters with the US President.

Mr Gates told the crowd he never met Mr Trump before he was elected to the Oval Office, and during the election campaign he “avoided him” at events.

But after Mr Trump secured the US presidency, Mr Gates revealed he had spoken with the President on two occasions – once at Trump Tower in New York City in December 2016 and again in March 2017 at the White House.

Bill Gates during his visit to Trump Tower in 2016. Photo: Getty

Mr Gates said on both occasions, Mr Trump asked him if HIV and HPV were the same thing.

He explained the newly elected president asked him if vaccines were a “bad thing” and Mr Trump told him he was exploring forming a commission to look into the “ill effects of vaccines”.

“I said, ‘No, that’s a dead end. That would be a bad thing. Don’t do that’,” Mr Gates recounted in the video.

“Both times he wanted to know if there was a difference between HIV and HPV, so I was able to explain those were rarely confused with each other,” Mr Gates said in subtly mocking tone.

Exclusive footage obtained by All In… Bill Gates dishes on his meetings with Donald Trump. More tonight at 8PM ET. #inners pic.twitter.com/Zoehj1WTfk

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

The philanthropist also spoke candidly of Mr Trump’s enthusiastic comments and knowledge of his 22-year-old daughter Jennifer Gates’ physical appearance.

Ms Gates is an elite equestrian competitor who has ridden against her father’s former tech rival, Apple founder Steve Job’s 19-year-old daughter, Eve Jobs, in horse-riding events.

Mr Gates explained Mr Trump had met Jennifer at a horse show in Florida in December and made a “grand entrance” on a helicopter despite speaking to his daughter 20 minutes earlier in the same location.

“… He knew my daughter Jennifer because Trump had this horse show thing down in Florida.

“In fact, he went up and talked to Jen and was being super nice and then 20 minutes later he flew in a helicopter into the same place.

“Clearly he had been driven away, but he wanted to make a grand entrance in a helicopter.”

Never before seen footage obtained exclusively by All In shows Bill Gates discussing meetings with Donald Trump #inners pic.twitter.com/GouJwYKghi

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

Mr Gates said when he first spoke to Mr Trump in December it was “kind of scary” how much he knew about his daughter’s “appearance”.

“Melinda didn’t like that too well,” Mr Gates said, referring to his wife and Jennifer’s mother, Melinda Gates.

The UK’s National Health Service website lists “What’s the difference between HPV and HIV” as one of its most common health questions.

It explains the human papilloma virus affects the skin and moist membranes and can cause problems such as verrucas, genital warts and abnormal cell changes in the cervix.

However, human immunodeficiency virus attacks the immune system and can lead to AIDS, but can be prevented with early diagnosis and treatment.