(Reuters) - Former President Donald Trump will be officially nominated next week at the Republican National Convention, a four-day event in Milwaukee, Wisconsin, aimed at firing up the party's base in the final stretch to the Nov. 5 presidential election.

The political gathering will feature televised speeches by rising Republican stars and Trump's choice for a running mate, while also highlighting the party's stance on topics such as abortion, immigration and the economy.

Here's what you need to know about the convention:

WHEN IS THE NATIONAL CONVENTION AND HOW DOES IT WORK?

The main action for the quadrennial event will be held from July 15-18 at the Fiserv Forum, an arena that is the home of the Milwaukee Bucks professional basketball team. More than 50,000 people, including hundreds of journalists from around the world, are expected to attend.

Party delegates from all 50 states and six U.S. territories will officially select nominees for president and vice president at the convention.

Trump secured the vast majority of delegates during the state-by-state Republican nominating process earlier this year, so his selection in Milwaukee is assured and considered a formality.

He is expected to accept the nomination with a speech on July 18, the final night of the convention. Trump is expected to pick his running mate by July 15, and the vice presidential candidate will then address the convention on July 17.

WHY IS THE LOCATION OF MILWAUKEE IMPORTANT?

Milwaukee is the largest city in Wisconsin, one of handful of swing states that will be important in determining the overall result of November's election.

The decision by Republicans to hold the convention in Wisconsin, which has chosen the candidate who won nationally in the last four elections, was no coincidence. President Joe Biden, a Democrat, won the state in 2020 by less than one percentage point, and public opinion polls show another closely fought race between him and Trump in Wisconsin this year.

The Republican Party's effort to showcase its support in Wisconsin took a hit ahead of the convention, with Trump reportedly calling Milwaukee a "horrible city" in a meeting with Republican lawmakers last month.

Trump campaign spokesperson Steven Cheung said Trump was referring to problems with crime and voter fraud in the city. Violent crime has been falling in Milwaukee, reflecting a trend across major U.S. cities. There was no evidence of widespread fraud in the 2020 or 2022 elections.

WHY DO PARTY CONVENTIONS MATTER?

Don't be distracted by the red, white and blue balloons and pageantry of the convention - the event is an opportunity for the party to get lots of free publicity and rally supporters across the country for an election that could hinge on turnout.

The party has not yet disclosed a detailed agenda, but the convention has historically been a time for leading figures and up-and-coming lawmakers to get valuable air-time to deliver potentially memorable speeches on the main stage.

The Republican National Committee has announced themes for each of the four days. Monday will focus on how Trump would "turn the page" on Biden's economic agenda; Tuesday will outline Trump's policies to target crime and support law enforcement; Wednesday will feature plans to stem immigration at the southern border and improve foreign policy; and Thursday will center on Trump's overall strategy for strengthening the country.

WHAT CHANGES WILL BE MADE TO THE PARTY'S POLICY PLATFORM?

The Republican Party's platform, a formal statement of policy positions, was approved by its platform committee and released on Monday. It is expected to be approved on the first day of the national convention next week.

The 16-page platform embraces Trump's position that the issue of abortion is to be determined by individual U.S. states. It makes no mention of a federal ban or protecting a fetus as a person under the U.S. Constitution - tenets that have been included in past platforms and were demanded by a cadre of influential evangelicals.

The platform, which is not binding, also pledges that Trump and Republicans will build a missile defense shield over the United States, carry out "the largest deportation in American history" of people in the country illegally, make permanent Trump's signature tax cuts and pass "large tax cuts for workers." It says they will demolish foreign drug cartels, protect Medicare and Social Security benefits, and support public funds being used for private school tuition.

WHEN IS THE DEMOCRATIC PARTY'S CONVENTION?

Democrats will hold their national convention in Chicago from Aug. 19-22.

Biden had a shaky debate performance against Trump on June 27, raising questions about whether the incumbent will be the party's nominee or be replaced by someone else.

It remains to be seen whether the convention will play a role in selecting a new candidate or whether Biden, who has vowed to stay in the race, will be officially made the nominee in Chicago.

Democrats are rolling out advertisements on more than 50 Milwaukee buses that will run through the Republican convention in an effort to criticize the party's policies and Trump, the Democratic National Committee said.

The ads focus on abortion rights, lowering the cost of prescription drugs and the recent criminal conviction of Trump, as well as his reported "horrible city" comment about Milwaukee.

(reporting by Nathan Layne in Wilton, Connecticut; Editing by Colleen Jenkins and Alistair Bell)

By Nathan Layne