Due to increased postal voting, some states, including Nevada and Pennsylvania, may not complete the presidential vote count today.
What usually happens? The US presidential election is not won by the popular national vote. The winner in each state collects electoral college votes - and needs a minimum of 270 to get the White House.
What is currently happening? Mainly due to the Covid-19 pandemic, a large number of voters - about 68%, compared to 34% in 2016 - voted earlier, including by mail. The counting of postal ballots is slower because the signatures and addresses of voters need to be checked. Some states start this verification process long before election day, but some other states do not allow it.
Which key countries are we talking about? Voting is not yet complete in five states: Alaska, Georgia, Nevada, North Carolina and Pennsylvania. The Associated Press, and even Fox News, have declared Joe Biden the winner in Arizona.

What else is complicating matters? Approximately half of all states will accept postal ballots that have arrived after election day as long as they bear the postmark no later than November 3rd. There were also reports of an increase in the number of people requesting a postal vote but then deciding to go to the polling station in person. They need careful scrutiny to make sure no one has voted twice.
The big unknown: The controversial result
In the 2000 race, Democratic nominee Al Gore lost Florida by just over 500 votes out of a total of nearly 6 million, which cost him the election. Following a controversial recount and a Supreme Court ruling, George W Bush was declared the winner.
Trump and his campaign this week have called for a halt to the vote count in Pennsylvania and Georgia, for which the Associated Press (AP) has not declared a winner. The Trump campaign has also called for a recount in Wisconsin, where the AP has declared Biden the winner. There is no evidence that legal campaign battles will have an impact on the outcome of the election.
Burimet: Guardian, USA Today