>>7820024
What is the symbol?
A symbol with five crosses like this is known as a Jerusalem Cross, and it was employed as the symbol of the Kingdom of Jerusalem from the 13th Century. The kingdom was established by crusading European Christians who invaded and conquered Muslim lands.
There is not one agreed meaning to the five crosses - various theories suggest they could represent Christ and the four gospels, five wounds suffered by Christ on the cross, or the four points of the compass.
The original symbol is likely to pre-date even the Kingdom of Jerusalem and was used in feudal states in what is now the country of Georgia, which since 2004 has used the five crosses on its national flag.
Why does Tom Steyer use it?
In an interview with BuzzFeed last year, before he announced he would run for president, Mr Steyer was asked about the significance of the cross on his hand.
"It means to tell the truth no matter what the cost is," he said. "For a while now, I have drawn it on my hand every day to remind myself to always tell the truth. I later discovered that it has traditionally been known as a Jerusalem cross."
He appears to have started drawing the symbol in the winter of 2017, and in May 2018, he told Politico it was a reminder to always tell the truth, even if you are put on the cross for it.
He also said it was the international sign of humility, although this is not established as a thing.
Listen to Tom Steyer on the BBC's Hardtalk programme
The key issues for 2020 Democrats
Mr Steyer - a long-term Democratic donor - is Christian, and this month told a podcast that he was 30 when he found God. But he has not drawn a link between his faith and the symbol on his hand.
Instead, his drive to "tell the truth" is tied to a political group he launched in October 2017, named Need to Impeach, that focused on removing President Donald Trump from office.
It's a message the 62-year-old has repeated since entering the race for the presidency last July. He has also condemned corporate interests that affect government policy, and vowed to declare a state of climate emergency on day one of his presidency, were he to be elected.
Who else uses it?
In recent years, images and terms associated with the Crusades in the Middle East have been appropriated by white supremacists.
When a white supremacist shot dead 50 people in mosques in Christchurch in New Zealand in March last year, his so-called manifesto was reported to include references to the Crusades.
Banners depicting the Jerusalem Cross, along with the term "Deus vult" (God wills it) that was associated with the Crusaders, were deployed by the far-right during a violent rally in Charlottesville, Virginia, in 2017.
As yet, however, the Jerusalem Cross has not been listed as a hate symbol by the influential Anti-Defamation League.