Every four years people in the US vote for who they want to be their president.
The president makes decisions about how the US is run and how it will work with other countries.
The person that is chosen is in charge of the world's biggest superpower.
Some people say that the American president is the most powerful person on Earth.
First, both of the main political parties - Republicans and Democrats - have to pick one candidate each who they want to run for president.
The parties choose their candidate by holding primaries or caucuses in each American state, which are held between January until about June.
In a primary election, the public vote for people called 'delegates' - who are supporting the particular person they want to run for president.
Each state has a certain number of delegates depending on many people live there.
If a candidate wins a state they get all that state's delegates.
'Super Tuesday' - held in February or March - is when many states vote in their primary elections.
The person from each party with the most delegates then becomes their candidate and runs for the job of president!
Some states use a caucus - a local meeting system - instead of holding primaries.
The presidential elections are always held on the first Tuesday in November.
Americans vote for people called 'electors' in their state who are supporting the candidate they want to be president - this process is called the electoral college.
The more people who live in a state, the more electors that state has. So California, which has lots of people living there, has 55 votes. While Delaware, where there aren't as many people, has just three votes.
In total, there are 538 votes across the 50 states and the capital, Washington DC.
The candidate with the most electors wins all the state's electoral college votes.
And the first candidate to win enough states to get to 270 electoral votes becomes the president.
The president of America can be a man or a woman of any race or any religion, but they must have:
- been born in the US
- be at least 35 years old
- have lived in the US for at least 14 years
It takes months, even years, of really hard work to be elected president. And you need a lot of money to support your campaign.
Once you've become president, the rules state one person can only be in the job for a maximum of eight years.