These two business veterans are going to be sharing the debate stage for the first time, as Fiorina was relegated to the pre-dinner debate in August. Her strong showing there gave her a boost in the polls, and CNN made a change to its rules so that she could get onto the main stage for this week’s debate.

There will other battles to watch, for sure. How will Ben Carson respond to the attacks that will come his way, given his surge? Will Rand Paul and Chris Christie spar over the NSA again? Will Jeb Bush manage to look like he wouldn’t rather be in Kennebunkport? But the fight between Trump and Fiorina is, in our mind, the main event, with the other scuffles being mere undercards.

Here are some fast facts about the dueling candidates:

BUSINESS EXPERIENCE

“Trump” has become so much more than just a name. It’s a powerful brand, standing for luxury and aspiration. Before he was a brand, though, Trump got his start as a real estate developer in New York City, taking over his father’s business. He is also involved heavily in the golf and casino businesses. He also leases out his name to slap on products, golf courses and more. Much has been made of the fact that multiple businesses owned by Trump have declared bankruptcy, though the candidate has argued bankruptcy isn’t in and of itself a bad thing.

Fiorina has a much more traditional business background. She began her career at AT&T, and eventually led the spinoff company Lucent Technologies before becoming the CEO of Hewlett-Packard in 1999. Her tenure at the company was rocky, with tens of thousands of layoffs and poor fiscal results. In 2005, HP’s board forced Fiorina to resign over disagreements about the company’s performance and direction.

POLITICAL RECORD

Which is better, no political experience or lackluster political experience? Trump clearly represents the “none” option here. Despite flirting with the idea of running for President going all the way back to the 1988 election — that’s right, 1988 — this is the first time Trump has ever actually appeared on a ballot.

Fiorina, meanwhile, ran for U.S. senate in California in 2010, losing to incumbent Barbara Boxer by 10 percentage points. Fiorina was also a major surrogate for John McCain in 2008, causing controversy when saying McCain’s ticketmate Sarah Palin couldn’t hack it as CEO of HP.

PRE-BOUT TRASH TALK

These two clearly don’t like each other. Trump has taken heat for saying of Fiorina in Rolling Stone, “Look at that face! Would anyone vote for that? Can you imagine that, the face of our next president?!”

A Fiorina PAC shot back with this ad:

Fiorina has also taken time to call Trump merely an “entertainer,” while calling herself a “leader.”