What to know on Election Day 2020: Culmination of the battle for the White House

Voters are casting their ballots nationwide Tuesday to choose whether the next president of the United States will be Donald Trump or Joe Biden, even as tens of millions have already voted either early or through the mail.

Here's everything you need to know for Election Day 2020 as Americans choose their next president.

Every election year so-called "battleground states" and their importance come to the forefront.

Because most states assign their Electoral College votes on a winner-take-all basis, this means states that are reliably red, like Oklahoma, or reliably blue, like California, are considered baked into each candidate's path to victory.

Therefore the candidates focus their time and effort on politically moderate states that could swing for one candidate or the other, and thus are likely to put them over the 270 electoral vote mark to secure the White House.

This year perhaps the most important battleground state is Pennsylvania, which provides a meaty 20 electoral votes and could provide an early indication of whether other Rust Belt states will swing for Trump or for Biden. If Trump can notch a win there -- and by extension potentially Michigan or Wisconsin -- it would put him on a very strong path to a second term.

In fact, because more states are likely in Biden's camp, according to polls, Trump will likely need to run the table with a large number of battleground states.