Millions of Americans tuned in to watch Oprah Winfrey's explosive interview with the Duke and Duchess of Sussex, Harry and Meghan, and some are wondering what the royals meant by some of the things they said.

So what is "The Firm" they referred to, why did Meghan hand over her passport, and is there really an HR department for the royals?

What sort of security do royals get?

The California couple say they were not offered a security detail for their newborn son Archie, and were therefore required to make deals to earn enough money to protect him.

"The Netflixes and Spotifys of it all was never part of the plan," Harry said, adding that his father Prince Charles cut him off financially last year.

The exact details of the royals' protection, which is paid for by the British public, is not widely known due to security reasons, says Robert Finch, Dominion Chairman of The Monarchist League of Canada, a monarchist advocacy organisation that promotes the Crown in Canada.

So there is a lot of speculation about what the truth is, he says.

"The degree of security depends on seniority and visibility of a royal - some are given protection only when performing official duties, not 24/7 - though some live within a protected cordon, such as Kensington Palace."

Within Scotland Yard, there is a Royal Protection Unit made up of uniformed and plain clothes officers.

Many people suspect that there is a specialist commando unit, possibly made up of SAS troops, that "shadows" the palaces occupied by the Queen "and possibly the homes of the two next heirs by generation [Prince Charles and the Duke of Cambridge] - as the threat level rises or falls", says Mr Finch.

"But this is never discussed."

Did Meghan have to give up her passport and driving licence?

"When I joined that family, that was the last time, until we came here, that I saw my passport, my driver's licence, my keys. All that gets turned over," Markle said in the interview, adding that those personal items were not returned until she left for California.

Buckingham Palace has yet to comment on the reason why such items may be held.

Historian and author Robert Lacey, who consults for Netflix series The Crown, says it was done for her own protection.

"Meghan had to hand in her driving licence under security rules," he says. "If she went out driving on her own, she would not be protected."

Author Marlene Koenig, who runs the website Royal Musings, says that the royals are given VIP treatment when they travel - they don't go through normal passport controls or wait for their baggage to be checked.

She says she can't imagine why her passport would be taken, but that it "would certainly have been requested when travelling on official tours".

Mr Finch says this is the first he's heard of this happening, "but one assumes that royals' valuable personal documents are kept in a safe or safes - under the eye of the overall palace security".

He says this may be done so the documents are not lost and are quickly available if a member of the Royal Family goes on tour.

"Sounds as if it fitted Meghan's narrative of being trapped and isolated, but really was routine, and probably anything would be accessible to her if she wanted it," he says.

Is there really a Human Resources department?

"I went to human resources, and I said, 'I just really - I need help'," says Meghan, adding that her request was denied since she is not a "paid employee of the institution".

"There's no HR department for working royals because it's a family affair," says BBC royal correspondent Jonny Dymond.

But there is an HR manager for lower level royal staff and the household, as set out on the Buckingham Palace website. Just not for senior household or staff.

Buckingham Palace says the HR department recently launched an investigation into Meghan over claims, which she denies, that she bullied several staff members into quitting.

It has not responded to the allegation that the same department refused to help her.

What did they mean by 'The Firm'?

Meghan and Harry made references to "The Firm" and the "institution" when discussing the Royal Family.

Meghan said: "It's a family business, right? So there's the family. And then there's the people that are running the institution."

There are competing theories on the origins of "The Firm" but it is widely credited to Prince Philip.

Author Marlene Koenig says it was created by the prince when he married the Princess Elizabeth in 1947.

"He likened to marrying into a family business or a family or a firm," she says.

But in her 2005 book The Firm: The Troubled Life of the House of Windsor, author Penny Junor writes that King George VI, who ruled from 1936 to 1952, "first referred to the House of Windsor as The Firm and the name stuck".

Mr Lacey, from The Crown, says that "'The Firm' has long been the nickname applied by the Royal Family to themselves. Meghan seems to have extended this to the staff, along with the word 'the institution'".

The "Firm" nickname now refers to everyone, from administrative to Royal Household staff who have "some sort of say in the life and work of the family", says Mr Finch.

He says it's unclear to whom Meghan was referring, but that it could include "friends of the royals or folk who, she perceives, have influence on them" - such as government officials.

How many people work for the Royal Family?

For some watching the interview, the references to the household, supporting departments and officials provided their first glimpse into the workings behind the scenes.

There are thousands of people that work to support the monarchy, including people who maintain art galleries and castles owned by the Royal Trust.

Each year, the Queen gifts each of her staff of around 1,500 with a traditional Christmas pudding.

Departments include the Private Secretary's Office, the Privy Purse and Treasurer's Office - which includes support functions such as HR and IT - the Master of the Household's Department, the Lord Chamberlain's Office and the Royal Collection Trust.